136 LAND AND FUESH-WATER MOLtUSCA OF THIRSK. 



Limneus pereger, Drap. Abundant in ditches and stagnant pools. The 

 varieties, acutus and laeustris, sometimes occur. 



Limneus stagnalis, Drap. Brick-ponds at Wood-end, near Thirslt. — J. Q. 

 Baker. Stagnant pond near Sowerby. 



Limneus palustris, Drap. Stagnant pond near Sowerby. — J. Q. Baker. 

 Brick-ponds between Thirsk and Topcliffe ! — J. Foggitt. 



Limneus truncatulus, Jeff. Not unfrequent. 



Limneus glaber. Gray. Amongst Lemna in a pond half-way between Whit- 

 suncliffe and Goi-mire. Pools on Pilmoor. — J. G. Baker. 



Ancylus fluviatilis, Mill. Adhering to stones in Whitelassbeck, near Thirsk; 

 in the Codbeck, and other localities. 



Velletia laeustris, Gray. My friend, J. W. Watson, found this species a few 

 yeai's ago, in a pond near Thirsk. We proceeded together to the place a 

 short time ago, but could not procure specimens; and I have since been 

 there alone, with a similar result. 



Physa fontinalis, Drap. Wood-end brick-ponds. — G. R. Baker. Frequent 

 in ditches at Newsham carr. 



Aplexus hypnorum, Gray. Ditch by the roadside, between Thirsk and Top- 

 cliffe, in considerable abundance ! — J. Foggitt. 



Planorhis corneus, Drap. Plentiful in a pond near Topcliffe. Sometimes 

 curiously deformed. 



Planorbis alhus, Mill. Pond between Kilvington and Feliskirk 



Panorbis marginatus, Drap. Very common in ponds and ditches. 



Planorbis spirorbis, Mill. Amongst Equiseta in a pond between Gormire 

 and Whitsuncliffe, and in the ditch on the roadside between Thirsk and 

 Topcliffe. 



Planorbis contortus, Mill. Plentiful in similar situations to the preceding. 



Cyclas cornea, Lam. In similaE situations. 



Pisidium pulchellum, Jen. Brick-ponds between Thirsk and Wood-end ! — 

 O. E. Baker. Ditches at Newsham carr 



Pisidium amnieum, Jen. Pond in the Hohnes, Thirsk ! — J. Foggitt. A 

 single immature specimen only. 



Anodon cygneus, Turt. Very abundant. Arriving at great perfection in 

 the Wood-end brick-ponds. 



Unio pietorum, Lam. In the lake at Studley park. — J. G. Baker. Mill-dam, 

 Codbeck, Thirsk, in considerable abundance. 



October 2Uh, 1854. 



