﻿I.AMPSILIS 



179 



The fijxiires in tlie Mission Scientifique represent adult males 

 probably, which are scarcely produced at all on the posterior 

 base, and have an evenly rounded posterior outline save for a 

 slight biangulation midw^ay up from the base. It is a more 

 evenly elliptical shell than umbrosa, but not so elongated as 

 Ik'ida. von Martens figures a smaller female shell, which he 

 refers to this species and this has a moderate marsupial swell- 

 ing. 



Group of Lampsilis metallica. 



Shell rather small, obovate-rhomboid, inflated, much narrow- 

 ed and rounded in front, the form approaching that of a 

 Modiolus; epidermis a rich coppery bronze, shining ; beak sculp- 

 ture consisting of two faint, rounded loops, the bars of which 

 are inclined to be nodulous; pseudocardinals compressed, not 

 well developed, and sometimes more or less broken into den- 

 ticles ; laterals distinct : pits in the beak cavity numerous and 

 very irregular; nacre dark, coppery to purple, with metallic 

 tints, iridescent behind. Animal unknown. 



Lampsilis metai.ijca (Say). 



Shell small for the group, scarcely inflated, thin but strong, 

 subrhomboidal, with a very faint post-dorsal wing, the hinder 

 part of the posterior slope obliquely truncated; beaks low, 

 rather full, with a few broken, doubly-looped ridges, the loops 

 rounded below ; posterior ridge high, very wide and rounded ; 

 surface nearly smooth, shining, metallic copper-colored ; left 

 valve with two subcompressed pseudocardinals and two deli- 

 cate, remote laterals ; right valve with one pseudocardinal, a 

 vestige of another above it and one lateral ; beak cavities shal- 

 low, containing a few indistinct pit marks ; nacre rich copper- 

 colored, iridescent and thinner behind. I have seen only what 

 I presume to be male shells of this somewhat rare species and 

 these are somewhat rhomboid, being truncated on the posterior 

 slope, the posterior end widely rounded below. The base line 

 is very slightly curved and the anterior end is rounded and 

 narrowed. 



T^ength 48, height 28, diam. 17 mm. 



