﻿28o NEPHRON A IAS 



what split or roughened pseudocardinals and two straiji^ht or 

 slightly curved laterals ; right valve with one pseudocardinal 

 and sometimes a vestigial one ahove it with one lateral ; there 

 are often indications of a low tooth between the two sets ; 

 beak cavities compressed, with several dorsal scars ; muscle 

 scars well impressed, the anterior ones rough ; nacre whit- 

 ish, rose or faint puq^le. scarcely thickened in front and show- 

 ing a feeble, radiating groove below the laterals. Male shell 

 with a straight or arcuate 1:)asc line ; that of the female a 

 little produced at the posterior base. 



Length 50. height 26, diam. 14 mm. 



Mexico. Palen(|ue. in the State of Chiapas. 

 iJnio calamitantm Mokici.KT, 'J'est. Noviss.. T. 1849, P- 30- — 



Fischer and Crosse. Miss. Sci.. TT, 1894. p. 612, pi. exhi, 



figs. 5. 5a. 

 Margaron [Unio) cnliinatorum Lea. Syn., 1870, p. 63. 

 Nephronaias calimatanim Simpson, Syn., 1900, p. 596. 

 Unio cnprinus von Martens, Biol. Cent. Amer., Moll.. 19CX), 



P- 505- 



According to Fischer and Crosse in the INTission Scientifique 

 the figure given by Sowerby is not typical, but a variety which 

 they call nephritica. Certainly this figure does not closely agree 

 with either their description or figures, and it looks to me like 

 that of a different species. Specimens in the National Mu- 

 seum from Palenque in Chiapas, Mexico, Morelet's locality 

 for this species, agree with the description of Fischer and 

 Crosse and their figure of what they call var. p?'olottgata. By 

 an oversight the name was misspelled in the Synopsis. 



Var. arc nans (Fischer and Crosse). 



Shell relatively short, oval, subtriangular ; posterior end at- 

 tenuated ; dorsal border arcuated. 



Length 47, height 27.5, diam. 17 mm. 

 Unio calamitartim var. arcuans Fischer and Crosse, Miss. 



Sci., IT, 1894, p. 613, pi. EXiv, figs. 5. 5a. 

 Unio cnpriniis var. arcuans von Martens, Biol. Cent. Amer.. 



Moll., 1900, p. 506. 



