﻿I.AM PSl LIS 175: 



hind at the end of the somewhat double posterior rid^e, the 

 extreme posterior point being- just below the median line. 



Length no, height 62 mm. : diameter not given. 



Rio Usnmasinto, Portugal, according to Reeve, who no 

 doubt intended this for Rio Usumacinta, Mexico, and Guate- 

 mala. 

 Unio testudineus Reeve. Conch. Icon., XVI, 1865, pi. xxii, fig- 



lOI. 



Unio explicatns Fischer and Crosse, Miss. Sci., Pt. 7, II, 



1894, p. 594. 

 LampsUis lividus Simpson, Syn.. 1900, p. 571. 



Very close to L. c.vplicata, Morelet, and believed to be that 

 species by Fischer and Crosse in the Mission Scientifique. It 

 is somewhat obovate, while the cxpUcata holds the same width 

 throughout ; it has much fuller, higher beaks, and Sowerby 

 states that it is a thin shell, while specimens of c.vplicata of the 

 size of Sowerby 's figure are rather solid. If his specimen is 

 a female, as I suspect it is, the marsupial swelling is less de- 

 veloped and quite different from that of c.vplicata. I have 

 recently seen a left valve of a shell sent by Dr. von Ihering 

 from the Rio Lacantun, Chiapas, Mexico, which agrees well 

 with Reeve's figure of U. testudineus and is more inflated and 

 less high than specimens of Lampsilis e.vplicata in the National 

 Museum collection. This valve measures 82 millimeters in 

 length, 43 in height, and shows the shell to be 28 millimeters 

 in diameter. I have no doubt but that it is the testudineus 

 of Reeve and that it differs from the L. c.vplicata of Morelet. 



Lampsilis expucata (Morelet). 



Shell large, subrhomboid or long elliptical, rather solid, sub- 

 inflated, with a large brown ligament ; beaks moderately full 

 and high, their sculpture scarcely developed : posterior ridge 

 moderate, sometimes rounded, sometimes a little angular ; sur- 

 face with concentric growth lines, which are strong anteriorly 

 but almost fade out in the middle of the shell ; color smoky- 

 brown, paler in young shells, darker in old specimens, the 

 unibonal region lighter and livid ; left valve with two small,. 



