Dr. J. Fj. Gi^jy on a new species of Sphserium. 25 



II. — On a second new species of Sphserium //'om the Paddington 

 Canal By Dr. J. E. Gray, F.R.S. &c. 



In company with the Spharium pallidum described in the last 

 Number of the ' Annals/ Mr. Rowse finds another species of the 

 genus which is very distinct from the well-known and generally 

 distributed Spharium corneum in being subtriangular, which 

 gives it much the external appearance of a species of Pisidium. 



I cannot identify it with any of the species in the British 

 Museum collection, nor can I find any description or figure re- 

 presenting it in any of the works on European freshwater Mol- 

 lusca ; I therefore indicate it as new. 



It most resembles some specimens which we have received as 

 Cyclas tumida of Pfeiffer, but I do not find any species under 

 that name in Dr. Pfeiffer's work. The Paddington Canal spe- 

 cimens are more inequilateral, longer, and more triangular, having 

 a very distinct hinder slope. 



M. Deshayes considers C. tumida as only a variety of S. cor- 

 neum. 



Spharium Pisidioides. 



Shell ovate, subtrigonal, involucres olive, pale edged, slightly 

 concentrically wrinkled, rather rounded in front, somewhat pro- 

 duced, with a broad subangular slope behind ; the umbones sub- 

 anterior, regularly convex. Siphons united nearly to the end, 

 the upper shorter, subconic ; apertures circular, simple, the lower 

 rather larger, about twice the length of the upper when expanded, 

 cylindrical ; the opening circular, simple. 



Hab. Paddington Canal. 



The adult shells are 6 lines long, 5 high, and 4 thick. They 

 have much the appearance of a large swollen Pisidium, but have 

 the two distinct siphons of the genus Sphcerium. 



The young shells which were deposited in the glass of water 

 during the night were much compressed and nearly regularly 

 oblong ; they varied in size, some being twice as large as the 

 others; the largest were about 1^ line long. 



When the siphons are very much extended the difference in 

 length between the two is not so great as above, as it is the 

 basal part of the siphons which appears to be the most extensile, 

 the apical parts keeping the same relative length to each other 

 that they did in the less extended state. 



I am informed that some British conchologists consider Sp. 

 pallidum to be the C. lacustris of Draparnaud : it is very unlike 

 the specimens I have received from France and the rest of Europe 

 under that name. 



