534 [proceedings of the academy op [Nov., 



Lampsilis tampicoensis (Lea). 



Unio tampicoensis Lea, Obs., II, p. 24. Von Martens, Biologia, p. 511, pi. 33, 

 fig. 1. 



Valles River at Mr. Willis' ranch, about halfway between Yalles and 



Pujal. 



Lampsilis moctezumensis n. sp. PI. XXV, figs. 1, 2, 3, 4. 



The shell is oblong, the dorsal and ventral margins both arched, the 

 former a little more so; altitude decidedly more than half the length, 

 diameter more than one-third the length; moderately strong but not 

 thick. The beaks are small and low. near the anterior fourth of the 

 length. In young shells they show one or two low, short undulations, 

 being nearly smooth. Color yellowish brown. Adult shells hardly 

 showing rays, even by transmitted light, but the young have narrow 

 green rays posteriorly, on a yellow ground, marked with dark concentric 

 streaks. Both ends are rounded. Sculpture of growth-wrinkles only, 

 weak on the middle of the valve, but rather emphatic anteriorly. The 

 interior is white, the nacre thinner and iridescent posteriorly. The 

 pseudocardinal teeth are moderately stout, blunt and nearly smooth. 

 In the left valve the posterior cardinal is larger than the anterior. 

 In the right valve the single cardinal is small. The lateral teeth are 

 short and widely separated from the cardinals. The cavity of the 

 beaks are rather deep. 



Length 68, alt. 38^, diam. 24 mm. 



Moctezuma River, State of San Luis Potosi. Very few specimens 

 were found. 



This species has some resemblance to spatulatus (Lea). It differs 

 from the related species by wanting corrugation on the posterior slope. 



Lampsilis iridella Pilsbry and Frierson. 



Nautilus, XXI, pi. 12, figs. 4, 5 (Dec, 1907) ; XXII, p. 81 (Dec, 1908). 



Very abundant in the Valles River at Valles and Mr. Willis' ranch. 

 Also taken in the Casas Viejas River, the Coy River, and Tampamolone 

 Creek. 



Most specimens from Valles are larger than the types, brownish- 

 yellow or olive-yellow with rays only on the posterior half, when adult, 

 or sometimes rays are entirely wanting. An adult shell measures, 

 length 61, alt. 31, diam. 19.5 mm. 

 Lampsilis semirasa n. sp. PI. XXVI, figs. 7, 8, 9. 



The shell is oblong-reniform, the ventral margin being a little 

 concave in the middle or straight, the upper margin strongly arched; 

 the posterior end is wider in female shells, scarcely so in males. The 

 altitude is contained about If times in length, diameter about 3 times 



