The hinge margin is generally straight. I have specimens, however, from 

 Alabama, Pennsylvania and Rhode Island, in which it is slightly curved. One 

 of the distinctive characters of this species is that the lateral teeth are never 

 placed at an angle with the cardinal teeth ; they are generally on a straight 

 line with them. 



The finest specimens I have seen of the Sph. s u 1 c a t u m were sent to me 

 by Mr. Ingalls, who had collected them in Washington Co., N. Y. ; they were 

 remarkably convex, and measured as much in length as 13-16ths of an inch ; the 

 beaks were very full, and much raised above the margin of the shell. 



This species was first described in 1818, by Lamarck, under the names of Cy- 

 clas s u 1 c a t a and Cyclas Saratoga a. Say, in 1819, ignorant that this shell 

 was known to conchologists, described it as the Cyclas s im i 1 i s, under which 

 name, until very recently, it has been most generally known. Say also fig- 

 ured this species, but his figure, I regret to say, is not correct, and would be 

 more apt to give one the idea of a Pisidium than of a Sphaerium. The descrip- 

 tion by Say of the Cyclas s i m i 1 i s applies perfectly to the shell under con- 

 sideration, of which Dr. Gould has given a very good figure in his Report on the 

 Invertebrata of Massachusetts. 



As related elsewhere,* I had an opportunity, some years since, while in 

 Paris, to see Lamarck's original specimens of the Cyclas s u Ic at a and S a r a- 

 togea, at the Garden of Plants, and at the Delessert Museum ; and to con- 

 vince myself by examination that they both belonged to one species, and were 

 identical with Say's Cyclas s i m i 1 i s. 



2. Sph. aureum, Prime. 



Cyclas aureua, Prime, Boston Proc. iv. 159, 1851. 



Animal, not observed. 



Shell transversely oval, slightly elongated, nearly equilateral, heavy, con- 

 vex ; beaks full, raised above the outline of the shell ; anterior margin broad 

 and rounded ; posterior narrower and somewhat angular ; inferior slightly 

 curved ; hinge margin somewhat broad, curved ; cardinal teeth diminutive, 

 double, so placed together as to represent the form of the letter V reversed, 

 and rather wide-spread ; lateral teeth situated each one at an angle with the 

 cardinal teeth, strong and large ; sulcations deep, not very regular ; epidermis 

 varying from a greenish yellow to a bright gold color, slightly lustrous ; inte- 

 rior of the valves bluish white. 



Long. 9-16 ; lat. 7-16 ; diam. 6-16 inches. 



Hab. North America, from Lake Superior ? 



(Cabinet. Agassiz and Prime.) 



This is one of our most attractive species, but also one of the rarest. It is 

 supposed to have been brought from Lake Superior by the expedition which 

 visited that region under Professor Agassiz. In general outline it offers some 

 similarities with the Sph. s u 1 c a t u m ; it is, however, a much more ponderous 

 shell ; it is less elongated, more convex, its sulcations are not so regular, its 

 color is different, and lastly, its hinge margin is much more curved. 



Compared to the Sph. s o 1 i d u 1 u m, it is more convex, more elongated, its 

 posterior margin is broader, the hinge margin is not so much curved, the beaks 

 are fuller, and the sulcations are not quite so heavy ; the color is also dif- 

 ferent. 



3. Sph. solidulum, Prime. 



Cyclas solidula, Prime, Bost. Proc. iv. 158, 1851. 

 C. distorta, Prime, loc. sub. cit. iv. 158, 1851. 



Notes on some American species of Cyclas, etc., by Temple Prime. The Hague, 

 1857. 8vo. 



