Skip to content

Cannibal slugs!

September 16, 2015

Early this morning I saw two Arion sp. slugs in convoy making their way across a path

Two Arions crossing a path

Two Arions crossing a path

The slugs weren’t in the process of copulation, which happens much farther up the body and involves a lot of mucus from what I’ve seen (!), so I was curious to know what was going on (and a bit suspicious because I don’t think I trust Arions to behave nicely). I pulled them apart and found, horrifyingly enough, that the rear slug had been chowing down on the (apparently unconcerned) front slug.

Arion with bitten rear end


Lovely things aren’t they? There is a mucus gland at the rear end of the slug, so it may be that the predator slug was acquiring nutrients the easy way, or it may have been a prelude to mating, or agggressive behaviour. It isn’t something I’ve seen before, but I’m told biting has been reported between Arionids.

Survey: Community Archaeology and Environmental Archaeologists

September 16, 2015

Dear all,

I’m conducting a brief (apparently it takes about 7 minutes to compete) survey to find out what (if any) interaction community archaeology groups are having with environmental archaeologists. If you are a member of a community archaeology group, please do answer the questions at before October 1st.

There will be a complementary survey for environmental archaeologists shortly.

Oyster shell inserts at Glastonbury Tor

June 11, 2015

Back in 2010, I presented a poster on shells in archaeological building materials at the International Council for Archaeozoology conference in Paris, which was published as a book chapter last year (you can read and download a proof copy here). One thing I mentioned was the use of oyster shell, especially the flat right valves of the oyster as a structural insert in between blocks of masonry. Yesterday morning I came across a striking example of this in the north eastern door of the ruined St Michael’s Tower on Glastonbury Tor, where there is a short series of oyster shells in a buff mortar matrix between two courses of masonry. These are very likely to be quite a late insertion, probably nineteenth century when some rebuilding work was done on the tower.

Right valves of European oyster (Ostrea edulis Linnaeus, 1758) used a structural inserts in masonry at St Michael's Tower, Glastonbury Tor

Right valves of European oyster (Ostrea edulis Linnaeus, 1758) used a structural inserts in masonry at St Michael’s Tower, Glastonbury Tor

[The Book of the British Countryside] Abbey

May 30, 2015


Abbey Barn and Abbey Farm in Yeovil. Built c.1420, but not a real abbey

Abbey Barn and Abbey Farm in Yeovil. Built c.1420, but not a real abbey

I don’t remember my first encounter with an abbey. Sherborne Abbey and Glastonbury Abbey are close to where I grew up, so it seems likely it was one of those. Yeovil has an Abbey Manor, an Abbot’s Mead, and an Abbey Farm, but there was never actually an abbey there (somewhere years ago I read that Abbey Farm had belonged to the Priory of Bermondsey – I forget my source, but I don’t think this is correct) .

As an archaeologist, my experience of abbeys has been quite limited. Not quite an abbey, which were large and powerful religious houses ruled by an abbot who was answerable only to the Pope (and perhaps a higher authority), there was a Carmelite friary on the site of the Colston Hall in Bristol, which I worked on as an excavator before the new theatre foyer was built. The late medieval landscape of Bristol between the Bearpit roundabout and the cathedral was dominated by religious houses. Traces are still there to be seen, most obviously the cathedral itself and St James’s Church by the bus station, but if you peer through gates between the two it is possible to catch occasional glimpses of an older cityscape. I find it quite hard to peel away the modern geography and visualise this monastic city.  There was also a convent in Clifton, rich in burials, where the wet red clay stained me and everything I touched a rich orange, so much so that a friend who passed me in town after work one day complimented me on my fantastic tan.

Most recently, and possibly coming full circle, earlier this year I worked on a shellfish assemblage from the Abbot’s Kitchen at Glastonbury Abbey (one of the most powerful abbeys) – dominated by oysters and whelks. That report is now online, and can be read here

Fragment of brown crab (Cancer pagarus) shell from Glastonbury Abbey

Fragment of brown crab (Cancer pagurus) shell from Glastonbury Abbey


[The Book of the British Countryside, first published by Drive Publications, the publishing arm of the Automobile Association in 1973, was a popular volume in 1980s Britain. It was essentially an encyclopedia that covered topics like geology, botany, zoology, archaeology, rural architecture and farming practices in an accessible style. I loved my parents’ copy, so much so that it has lost its cover, and still consult it after a day walking. It was a huge influence on me growing up. I am attempting a series of posts about my personal reflections on the entries in the book. I don’t honestly have very much to say about “Acacia” or “Aconite, Winter”, which are the other two entries on the first page. I did see two false acacia trees in bloom today though. I’m not sure I’ve ever seen a winter aconite though.]

Beachcombing for bioarchaeology

February 10, 2015

On Saturday I took a walk along the beach from Preston to Weymouth in Dorset, looking for shells and other invertebrate remains to identify and add to my reference collection. Building a collection of modern material is important, as it is much better to have physical examples for comparison than pictures online or in books. Looking at my collection, I had last visited these beaches in 2008, when I found numerous slipper limpets (Crepidula fornicata). These aren’t particularly useful for British archaeology, as they are an accidental introduction from North America which arrived during the nineteenth century when a new species of oyster was imported from the United States to be grown in British waters. They are significant in the ecosystem however. They eat plankton either in suspension in the water or in deposits, and can out-compete many native molluscs including our native oyster Ostrea edulis. They are often found stacked on top of one another – the oldest animals at the base of the stack are females, the youngest at the top males. When females die, the males nearest the bottom become female.

Chain of Crepidula fornicata on Weymouth beach.

Chain of Crepidula fornicata on Weymouth beach.

Despite the dominance of slipper limpets, a few other species were to be found, especially on Weymouth beach. Mollusc shells included the queen scallop Aequipecten opercularis, the dog cockle Glycymeris glycymeris, the great top shell Gibbula magus, the common otter shell Lutraria lutraria, and the common whelk Buccinum undatum.

Great top shell (Gibbula magus) from Preston beach

Great top shell (Gibbula magus) from Preston beach

As well as mollusc shells, I was looking for bryozoans. These are colony-forming invertebrates that are quite often found on marine shells from archaeological sites, and occasionally in sediments on coastal sites too. Identifying the species on shells may help identify the region or environment from which the shell was harvested. Back in 2013, I published a (now happily open access) paper reviewing bryozoans in archaeology, and I was keen to build up my reference collection.

On a frond of Fucus seaweed, I found a colony of Electra pilosa, a relatively common lower shore species found on all British coasts.

Electra pilosa on a Fucus frond

The zooids (individual animals) of this particular colony had especially pronounced medial proximal spines looking rather like bristles:

Electra pilosa zooids

Electra pilosa zooids.

The inner surface of the otter shell I found was also home to two species of bryozoa – Plagioecia patina, which forms disc-shaped colonies and is found in shallow water on all British coasts, and Tubulipora plumosa, which is also found on all British coasts. Along with these were long tubes secreted by the worm Pomatoceros triqueter. In his 1978 report on the shells from the Graveney boat, Ken Thomas noted that the presence of organisms on the inner surface of a shell from an archaeological context suggests that it was already an empty shell at the time it was collected from the shore, meaning it is not food waste, so may have arrived at a site as a curio or for some other reason.

Common otter shell (Lutraria lutraria) showing bryozoans and worm tubes

Common otter shell (Lutraria lutraria) showing bryozoans and worm tubes

Colony of Tubulipora plumosa

Colony of Tubulipora plumosa


Colony of Plagioecia patina

Penmyarth Fish Stone/ Llangorse/ Crug Hywel

May 24, 2014

This will be the fourth year that I have worked at the Green Man Festival for what has become Guerilla Archaeology. The festival, which takes place in August, is held at Glanusk Park on the banks of the River Usk near Crickhowell. It is a rich archaeological landscape, and Alan Lane and I have written a brief guide to the archaeology of the Park and its environs, which is available as an information board during the festival. The major prehistoric monument of the Park, the Fish Stone, is not accessible to the public, however, nor is it accessible during the festival. Having never seen it, I wrote to the Park’s estates office and asked to visit. A number of other Guerilla Archaeologists were able to come. Alan Lane kindly agreed to extend the trip with a guided visit to the crannog at Llangorse, and Jacqui Mulville suggested we climb to the hillfort on Table Mountain,Crug Hywel.


Standing at just over 4.2 metres tall, the Fish Stone is an Old Red Sandstone orthostat which looks somewhat like a fish. It is sited in a quiet glade on the banks of the Usk. The worn face in the photo above faces east towards Crickhowell – as Ian Dennis noted, at sunrise and sunset the stone must cast a long shadow of a fish on the ground, while at noon a thin shadow will point due north. It is believed to be Bronze Age, and to form part of a possible group of route markers. There is another standing stone in Glanusk Park – this one is thought to have been early medieval, although it has been moved to a new location in Penmyarth churchyard and engraved with an epitaph to Joseph Henry Russell, the 2nd Baron Glanusk, in 1928.


ImageStanding stone in Penmyarth churchyard

After Glanusk Park, we headed off to Llangorse lake, site of the only crannog in Wales. A visitor centre tells the story of the archaeology – with the pallisaded settlement being built in the late 9th century AD, and periodically extended, until being destroyed in 916 by an army led by Aethelflaed, Queen of Mercia (and King Alfred’s daughter). The reconstructed roundhouse that houses the visitor centre is based on an iron age crannog house from Scotland or Ireland, rather than any of the Llangorse structures. Chained outside the visitor centre is a reconstruction from the 1990s by Time Team of a log boat discovered in the lake. To reach the crannog itself, we hired rowing boats. The site is protected by a stone bund, and there is little to see of the archaeology, although we could make out some planks in the shallow water to the south east of the crannog


The south east of the crannog at Llangorse

After lunch in Crickhowell, we climbed up to Crug Hywel hillfort on Table Mountain, a spur of Pen Cerrig Calch. Walkers are damaging the site by taking stones from the banks to build shelters – two of these were extant when we visited. The hillfort encloses an area of 162 x 59 metres, and has frankly stunning views . A small number of rounded hollows are visible which may be hut sites.


The entrance to Crug Hywel, at the east of the hillfort, and just a little taste of the fabulous views.