NON-MARINE MOLLUSCA SURVEY,
1986
I. J. KILLEEN
Progress on t h e survey d u r i n g 1986 was n o t as good as originally h o p e d f o r . Less t h a n 100 n e w t e t r a d s w e r e r e c o r d e d , m a k i n g a total of 740 that have b e e n e x a m i n e d to d a t e . T w o large a r e a s r e m a i n sparsely r e c o r d e d : the B r e c k l a n d a n d t h e a r e a t o t h e n o r t h of L o w e s t o f t . A n e f f o r t must b e m a d e to fill in the m a i n gaps d u r i n g 1987 and ideally to t a k e t h e survey to c o m p l e t i o n . H o w e v e r , m a n y interesting n e w r e c o r d s w e r e o b t a i n e d in 1986, including t h r e e n e w vice-county records: Vertigo substriata ( J e f f r e y s ) . T h e r e w e r e five n e w sites for this locally r a r e species. It w a s f o u n d living in a small a r e a of relict acid f e n (TM4570) and an a d j o i n i n g w e t w o o d l a n d ( T M 4 6 7 0 ) to t h e west of D u n w i c h . T w o o t h e r scarce species, Vertigo antivertigo and Columella edentula w e r e f o u n d in association. T h e o t h e r sites w e r e all in t h e n o r t h - w e s t of t h e c o u n t y , t w o at E l v e d e n on w o o d e d h e d g e b a n k s (TL8389 and T L 8 3 8 0 ) and at S a n t o n D o w n h a m (see b e l o w ) . It s e e m s likely that f u r t h e r sites f o r V. substriata will be discovered in suitable h a b i t a t s in t h e B r e c k l a n d a r e a . Vertigo pusilla M Ăź l l e r . T h e only previous West S u f f o l k record in t h e last 50 years is at W e s t Stow on a dry ivy-covered wall, a quite typical h a b i t a t for this species. T h e discovery of a thriving colony at S a n t o n D o w n h a m (TL8086) associated with V. substriata and Columella aspera was quite surprising. S p e c i m e n s of all t h r e e species w e r e sieved f r o m leaf litter a r o u n d an old tree s t u m p in t h e marginal a r e a of oak a n d silver birch s u r r o u n d i n g a conifer forest. H o w e v e r , V. pusilla r e m a i n s a very r a r e species in t h e c o u n t y . Vertigo angustior J e f f r e y s . O n e very f r e s h shell f o u n d at M a r k e t W e s t o n F e n (TL9878). T h i s r e p r e s e n t s only t h e sixth site in Britain w h e r e this declining species is c u r r e n t l y r e c o r d e d living. T h e s p e c i m e n was sieved f r o m sedge debris in an a r e a of recently cut Cladium mariscus d u r i n g a field excursion by t h e C o n c h o l o g i c a l Society of G r e a t Britain. F u r t h e r searching on t h a t and a s u b s e q u e n t visit failed to yield f u r t h e r s p e c i m e n s . This would suggest that this snail is e i t h e r living at e x t r e m e l y low density a n d / o r t h e w r o n g a r e a was being s e a r c h e d . T h e typical habitat f o r Vertigo angustior is w e t , m a r s h y grassland o r d a m p , mossy hollows in s a n d d u n e s . H e n c e , the Cladium b e d s o n t h e f e n w o u l d a p p e a r to b e t o o wet f o r this species. It is possible that t h e s p e c i m e n f o u n d m a y h a v e b e e n t r a n s p o r t e d into t h e sedge b e d s f r o m t h e slightly d r i e r grassland margins. F u r t h e r work is r e q u i r e d to establish t h e exact status of V. angustior at M a r k e t W e s t o n F e n . It is w o r t h stressing t h e i m p o r t a n c e of M a r k e t W e s t o n F e n as an o u t s t a n d ing e x a m p l e of a h a b i t a t of its type. T h e mollusc f a u n a of t h e f e n is very rieh and includes several locally r a r e and e n v i r o n m e n t a l l y sensitive species, in fact t h e site could fully justify being a reserve o n t h e basis of its Mollusca a l o n e . It is very i m p o r t a n t that these f a c t o r s should b e t a k e n i n t o a c c o u n t w h e n p l a n n i n g f u t u r e p r o g r a m m e s of m a n a g e m e n t a n d c o n s e r v a t i o n .
Trans. Suffolk
Nat. Soc. 23