538 PROCEEDINGS OF THE ACADEMY OF [NOV., 



Length 78, alt. 43.5, diam. 22.5 mm. 



Casas Viejas River, State of San Luis Potosi. 



With some resemblance to L. moctezumensis, this species differs by 

 the slight corrugation of the posterior slope and the more compressed 

 form. Some young specimens (pi. XXVII, fig. 7) from the type locality, 

 which seem referable to this species, have the whole valves ornamented 

 with wide green rays. The beaks have a minute area sculptured with 

 about four concentric wrinkles, which are very weakly bilobed. Outside 

 of this sculptured portion the green rays are very distinct, as in allied 

 species. A faint rib or green stripe radiates from the beak in the 

 middle of the posterior slope, which is in part obliquely corrugated. 

 These specimens measure from 17^ to 36 mm. long. 



Lampsilis coyensis n. sp. PI. XXVII, figs. 3, 4. 



The shell is oblong, with beaks at the anterior fourth of its length ; 

 slightly wider posteriorly, the posterior end sloping above, bi angular 

 below; anterior end rounded; basal outline moderately curved, convex. 

 There is a rather distinct angulation from the beak towards the 

 posterior-basal angle, and the indistinct trace of a ridge to the posterior- 

 median angle. The beaks are low, with minute, recurved tips sculp- 

 tured with a few coarse double-festooned wrinkles, the connection 

 between the two curves almost interrupted. The sculptured portion 

 is not quite two mm. long. Subsequent growth is marked with growth- 

 lines only, or with a very slight oblique corrugation in places on the 

 posterior slope. The epidermis is rather smooth but not gloss}^ and 

 is shortly and finely lamellose towards the margins. Color obscure 

 greenish yellow, indistinctly marked all over with green rays. Near 

 the beaks the rays are very distinct on a light ground. By transmitted 

 light it is light yellowish, very profusely marked with green rays. 

 The interior is white and somewhat thick anteriorly, thin, blue and 

 slightly iridescent in the posterior half. The teeth are moderately 

 strong. 



Length 36, alt. 21, diam. 13.5 mm. 



Coy River, State of San Luis Potosi, Mexico, collected by Mr. A. A. 

 Hinkley, January, 1909. 



These Lampsilis from the Coy River were found where there was a 

 long mosslike plant growing, the current of the stream keeping it 

 in a constant waving motion. The water was two to four feet deep. 

 The Lampsilis were found by feeling in the roots of this moss. 



On the moss and bed of the stream were Pachycheilus and Litha- 

 siopsis, but the former were more numerous lower down the stream 

 in a small recess where there was no current. In this recess were also 



