26 DESCRIPTION OF FIFTY-TWO SPECIES OF UNIONID^. 



young yellowish, with green rays behind, with scarcely perceptible lines of growth; 

 umbonial slope rounded; posterior slope carinate, compressed, with two well-marked 

 impressed lines from beaks to margin ; cardinal teeth small, compressed, crenulate 

 and disposed to be double in both valves ; lateral teeth rather long, lamellar and 

 slightly curved; anterior cicatrices distinct; posterior cicatrices confluent and mode- 

 rately impressed ; dorsal cicatrices placed nearly in the centre of the cavity of the 

 beaks ; cavity of the shell somewhat deep ; cavity of the beaks rather shallow and 

 obtusely angular; nacre silver white and very iridescent. 



Soft Parts. — No ova were found in the ovaries or branchial uterus. Branchia 

 rather small, inner one the larger, curved below, free the whole length of abdominal 

 sac. Palpi large, round below, united near to the top. Mantle very thin, thicker 

 and colored at the margin. Branchial Opening rather large, light brown, with nu- 

 merous small papillfe. Aiial Opening large, dark brown, with numerous very minute 

 papillse on inner edges. Super-Anal Opening very small, colored, united below- 

 color of the mass whitish. 



BemarJcs. — I have before me a number of specimens of different ages. This 

 species has a general resemblance to the Nicaraguan species, and is somewhat like 

 Eowellii (nobis), but may be distinguished by the difference of outline, Macnielii 

 beino- oblong, having nearly the outline of Scamnatus Morelet, from Cuba. I have 

 pleasure in calling it after Mr. McNiel, who discovered it while travelling in Cen- 

 tral America. I owe to the liberality of the Peabody Acad. Nat. Sci. of Salem 

 the possession of specimens and the privilege of describing the species. 



Unio Pealei. pi. 8, fig. 23. 



Testa Iffivi, rotunda, valde inflata, subglobosa, valde in^quilaterali, antice et postice rotundata ; val- 

 vulis crassis, antice crassioribus ; natibus elevatis, tumidis, subretusis; epidermide luteo-olivacea, 

 dilute perradiata ; dentibus cardinalibus paviusculis, subconicis ; lateralibus longis, crassis sub- 

 rectisque ; magarita argeatea et iridescente. 



Shell smooth, round, very much inflated, subglobose, very inequilateral, round 

 before and behind ; valves thick, thicker before ; beaks raised, swollen and some- 

 what retuse ; epidermis pale olive with rather indistinct rays over the whole disk ; 

 cardinal teeth rather small, subcorneal; lateral teeth long, thick and nearly 

 straight; nacre silver white and iridescent. 

 Proc. Acad. Nat. Sci., 1871, p. 191. 



lTa&.— Kansas, Mr. C. W. Peale. 



Cabinet Academy Natural Sciences. 

 Diam. 1-2, Length I'T, Breadth 2 inches. 



