﻿LAMPSILIS 191 



CtToup of Lampsilis scutulata. 



Shell rhombic elliptical, compressed, rather thin, with a high 

 posterior and a low anterior wing, with two posterior ridges ; 

 the valves often exhibiting fine radiating plications on the pos- 

 terior part ; beaks compressed but very sharp pointed, some- 

 times showing the nepionic shell, almost destitute of sculpture, 

 which, when present, consists of faint indications of two round- 

 ed loops ; epidermis rather dull, sometimies indistinctly rayed ; 

 left valve with two pseudocardinals, the anterior a sharp, 

 straight ridge sloping obliquely downward and forward from 

 a point just in front of the beaks, the hinder curiously com- 

 pressed and showing a tendency to break into denticles ; right 

 valve with two sharp, ridge-like, sloping pseudocardinals ; lat- 

 erals slender, compressed, straight, or wavy ; nacre bluish-white 

 to pale violet ; dorsal scars few ; female shell apparently slightly 

 swollen at the posterior base ; animal unknown. 



Lampsiijs scutulata (Morelet). 



Shell elliptical or elliptic-rhomboid, compressed, thin, green 

 or light olive-green, with a few faint rays, with a low but dis- 

 tinct, somewhat angled posterior ridge, which is sometimes 

 double ; surface of the posterior half of the shell with slightly 

 curved, nearly vertical plications ; beaks low, not inflated ; pos- 

 terior wing well developed, angled behind ; left valve with two 

 pseudocardinals, the posterior small, and two laterals; right 

 valve with two compressed pseudocardinals and one lateral ; 

 nacre bluish on the border, yellowish in the centre of the shell. 

 Both male and female shells are somewhat rhomboid, the for- 

 mer more tnmcated at the posterior slope. The male shell ends 

 in a blunt point, but a short distance above the base, and the 

 base line is nearly evenly curved ; the female shell is biangulate 

 behind and has a well-developed marsupial swelling at some 

 distance in front of the posterior end. 



Length 49, height 30, diam. 16 mm. 



Yucatan. 



