Worcestershire Record No. 23 November 2007 pp. 54-71

PROVISIONAL ATLAS OF LAND SNAILS IN SOUTH-EAST WORCESTERSHIRE

Terry Knight

Area of survey

     The area sampled is shown in Figure 1. This comprised the parts of present Worcestershire in OS 10km grid squares SP03, SP13, SP14, SP15 plus those parts in squares SP05 and SP04 south and east of the rivers Avon and Isbourne. Also included was the area of the Cotswold plateau around Seven Wells and Spring Hill which used to be in the parish of Broadway but is now in Gloucestershire. A few of the monads (1 km by 1 km squares) around the boundary were not visited. These were SP0436, SP0835, SP1334, SP1342, SP1444, SP0447 and SP0446. In all a total of 156 monads were sampled

Sampling

This was done between February 2006 and August 2007, but most was done in the months of February and March in each of the two years. The object of the survey was to get as even coverage of the area as practical. Details of the sampling are given in Table 1. Individuals examined consisted mainly of fresh shells but also some live animals and a few weathered shells. The few specimens of Oxyloma/Succinea encountered were ignored due to the difficulty of identification. Fens, marshes and spring oozes occur only rarely in the survey area and were not searched.

Type

Samples

Individuals (approx)

Details

       

L

96

1500

Loose soil and tree and other surface debris sample of average dry weight of about 400 gm generally from two monads (1 km squares) per tetrad

R

136

4100

A five minute collection from a roadside in practically all monads in which there was a road

T

33

1000

Collections over about 20 minutes from a railway in most monads having one

V

8

135

A set of special samples from the base of stone walls in monad SP0849

W

21

21

Collections over about 20 minutes from walls (mostly stone) and retaining walls in each monad having a significant number of stone walls.

X

87

2050

Additional collections from the surface, under stones and logs from most monads having less than two other samples.

(Sum)

381

9100

 

Table 1. Details of sampling see text.

Results

The number of species discovered during this limited survey was high, particularly in the north-west (Cleeve Prior and the Littletons) and in the south-east (Broadway). Figures 2 to 5 show the distribution maps and histograms for the number of species both per monad and per tetrad (2 km by 2 km squares). The number of species varied from 2 to 22 per monad and from 6 to 31 per tetrad. Cleeve Prior and the Littletons area was significantly richer in snails than elsewhere with tetrad SP0646/SP0747 being very significantly richer.

Species accounts

Names, size ranges, status, British distributions and a few other details were taken from Kerney, 1999.

Drawings

These were all based on specimens from the survey area. Where a single drawing is given per species, this is life size. Elsewhere two drawings are given, the left-hand one being enlarged and the right-hand one, in the circle, being life size.

Distribution maps

A symbol on the map denotes at least one individual (shell or live animal) was found in the monad during the survey. A black square indicates that at least one individual was found in an area not usually subject to flooding, a black triangle indicates that individuals found in the monad were all in samples from areas normally subject to flooding.

Acknowledgements

I would like to thank Rosemary Hill for confirming some identifications and Harry Green for arranging this. Also Alison Ward, Betty Ballard and John Tilt for help in colour descriptions.

Reference

KERNEY, M. 1999 Atlas of the Land and Freshwater Molluscs of Britain and Ireland. Harley Books.

The 48 species accounts and distribution maps follow.

Distribution maps and histograms for the number of species (Figs. 1 to 5)
Helix aspersa, Cepaea hortensis, Cepaea nemoralis
Helicogona lapicida, Arianta arbustorum, Trichia hispida
Trichia plebeia, Trichia striolata, Hygromia cinctella
Perforatella subrufescens, Monacha cantiana, Helicella itala
Cernuella virgata, Candidula gigaxii, Candidula intersecta
Balea perversa, Clausilia bidentata, Cochlodina laminata
Cecilioides acicula, Euconulus fulvus, Oxychilus helveticus
Oxychilus allarius, Oxychilus cellarius, Oxychilus draparnaudi
Aegopinella nitidula, Aegopinella pura, Nesovitrea hammonis
Vitrea contracta, Vitrea crystallina, Vitrina pellucida
Discus rotundatus, Punctum pygmaeum, Ena obscura
Acanthinula aculeata, Vallonia excentrica, Vallonia pulchella
Vallonia costata, Lauria cylindracea, Pupilla muscorum
Vertigo pygmaea, Vertigo pusilla, Pyramidula rupestris
Cochlichopa lubricella, Cochlichopa lubrica, Azeca goodalli
Carychium tridentatum, Carychium minimum, Acicula fusca
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