﻿r.AMPSILIS 



177 



has two obtuse, somewhat indistinct diverging lines. The spe- 

 cies is from the Chixoy River, in Guatemala, and dedicated to 

 Dr. Carl Sapper, who has collected, in scientific expeditions in 

 Central America and Mexico, many interesting Unionidcc, for 

 which I am much indebted to him." (von Ihering.) 

 Lampsilis explicatus, Simpson, Syn., 1900, p. 571, n. 4. 

 Lampsilis sapperi von Ihering, Naut., XV, 1901, p. 50. 



Lampsilis fimbriata Frierson. 



"Shell large, elliptical, thin and compressed. Dorsal line in- 

 curved in front of the beaks. Anterior margin somewhat ob- 

 truding, obtusely pointed or sharply elliptically curved. Basal 

 margin nearly straight, occasionally slightly arcuated. Poste- 

 rior margin broadly, roundly biangular. Beaks low and with- 

 out sculpture. Posterior ridge elevated, rounded and obsolete. 

 The greatest diameter of the shell being about the center of 

 the ridge. Sides flattened and generally somewhat constrictec' 

 in the middle. Behind the posterior ridge, down the siphonal 

 area extends a raised line, enclosing a triangular area, (having 

 its apex at the beak), which is sculptured with small pustules 

 arranged in upturned lines. Epidennis yellowy horn-color, 

 sometimes obsoletely rayed on the posterior slope. The shell 

 would seem to be nearly smooth, but in all the specimens seen 

 there are numerous irregular, radial, pit-like impressions and 

 concentric striae and shallow sulci. The radial impressions, or 

 pits, extend through the shell and are visible inside and out. 

 Hinge ligament stout and rather long. Muscle scars well 

 marked, separate in front and confluent behind. Teeth stout, 

 double in the left and single in the right valve. Beak cavities 

 shallow, with a row of muscle scars running downward, for- 

 ward and onto the base of the cardinal tooth. Nacre white, 

 flesh-color or dark purple, very irregularly laid on and very 

 thin. Except in old shells, the prismatic structure extends far 

 beyond the nacre and the epidermal layer, in turn, extends still 

 further. 



Length 80, height 47, diam. 25 mm." (Frierson.) 



Type locality, Valles River, Mexico. 



