15 



Animal not observed. Shell small, ovate-oblong, moderately inflated, ine- 

 quilateral, translucent ; anterior and basal margins rounded, posterior some- 

 what distended and subtruncate ; beaks inclined towards the anterior, promi- 

 nent, calyculate ; valves slight, convex ; epidermis dark yellow, irregularly 

 spotted with a darker color ; striae hardly visible ; teeth very small ; hinge 

 margin somewhat curved, very narrow. 



Long. 5-16 ; lat. 3-16 ; diam. 5-32 inches. 



Hab. S. America, in Brazil and Venezuela. (Cabinets Acad. Nat. Sci. 

 Phila., Bourguignat, Gassies, Museum of Paris, Michaud, and Museum at 

 Ley den.) 



The specimen from which this description was prepared the original shell 

 from which Mr. Haldeman described the Pisid. diaphann m is in the 

 Cabinet of the Academy of Natural Sciences of Philadelphia. It was dis- 

 covered in the interior of a large Ampullaria from Brazil. I have never seen 

 the Cyclas modioliformisor the Pisid. Moquinianum, but judging 

 from their descriptions and from the figure of the latter, I have little doubt 

 but that they belong to the same species. I have had occasion to examine 

 the Cyclas striatella, littoralis and Venezuelensis personally. 



The Sph. modioliforme seems to be rare. It bears some resemblance 

 to the Sph. meridionale, but it differs from it in being more inflated and 

 of a lighter color. 



26. Sph. meridionale, Prime, Proc. Acad. Nat. Sci. Phila., 1861. 

 Animal not observed. Shell small, transversely-oblong, compressed, deli- 

 cate, inequilateral ; anterior side narrow, shorter ; anterior margin somewhat 

 angular, posterior subabrupt, basal slightly rounded ; beaks inclined towards 

 the anterior, small, calyculate, approximate at apex ; valves slight, com- 

 pressed, striae very regular and delicate, hardly perceptible ; epidermis yel- 

 lowish brown, irregularly mottled with large blotches of a much darker color ; 

 hinge margin very slightly rounded, narrow, much shorter than the basal 

 margin ; cardinal teeth diminutive ; lateral teeth slight, the posterior tooth 

 much the more elongated. 



Long. ^ ; lat. 1-5 ; diam. 2-16 inches. 



Hab. N. America, at Panama. (Cabinet Prime.) 



This species, of which I have never seen but one specimen, is easily dis- 

 tinguished by its very inequilateral and compressed shape. Compared to the 

 Sph. m a c u 1 a tu m , it is larger, its posterior margin is less abrupt, and its 

 lateral teeth are larger. 



27. Sph. maculatum, Morelet. 



Cyclas maculata, Morelet, Test. nov. lusul. Cub., etc., pt. 2d, 25, 1851. 



Animal not observed. Shell small, transversely-oblong, rhombic, elongated, 

 inequilateral, compressed, delicate ; anterior side much the narrower, slightly 

 rounded ; posterior side very broad ; posterior margin abrupt, forming a 

 straight line from the hinge to the base of the shell ; inferior margin nearly 

 straight ; valves slight, very little convex ; beaks small, calyculate, inclined 

 towards the anterior side ; striae not perceptible ; epidermis dark yellowish- 

 brown, irregularly mottled with spots of a much darker color ; hinge margin 

 nearly straight ; cardinal teeth very small ; lateral teeth strong, elongated. 



Long. 4-16 ; lat. 3-16 ; diam. 2-16 inches. 



Hab. N. America, in Yucatan. (Cabinets Morelet, Jay and Prime.) 



A rare species ; the only specimens I have met with were kindly presented 

 to me by the original describer. It is easily distinguished from all other 

 species of Sphserium by the very great disproportion which exists between 

 the lateral margins. 



