THE NAUTILUS. 113 



marked; anterior part somewhat angular with the end rounded; 

 posterior end rounded or slightly truncate, inferior margin regu- 

 larly curved ; shell thin, translucent, colorless to pale horn ; sur- 

 face very finely, almost regularly striated, somewhat shining; inte- 

 rior surface with fine but well marked, crowded pit?, visible from 

 the outside; hinge rather fine, plate narrow, cardinal teeth rather 

 short but high, lamellar, the right one almost straight and longitu- 

 dinal in its anterior part, thickened in the posterior and curved 

 downward beyond the level of the plate ; those of the left valve 

 little curved, the inferior somewhat the larger and projecting down- 

 ward over the edge of the hinge plate ; lateral teeth rather small 

 and thin, pointed in the middle and rathor abrupt, in the right valve 

 the anterior much the largest, slightly-projecting inward. 



Long. 2-5, alt. 2-3, diam. T7 mill. (Texas). 



Long. 3-3, alt. 2'8, diam. 2'4 mill. (Mexico). 



Habitat : Texas, Mexico. 



In shape, color and striation, it has some resemblance with P. 

 punctatum, but the latter is much smaller, its surface is microscopi- 

 cally rugulose, dull, and the hinge comparatively stouter. 



It was first seen in drift materials from the Guadaloupe River, 

 Comal Co., Texas, collected and kindly sent by Mr. J. A. Singley 

 in 1892, represented by a fair number of specimens in all stages of 

 growth. Then in drift from the same river, sent by Mr. Wm. A. 

 Marsh, a few young specimens. Another lot from the Guadaloupe 

 River is in the U. S. National Museum (No. 134,010, Gurley), and 

 under the same head must be ranged one from Itzlan Creek, Gua- 

 daljara, Mexico, (No. 102,215). Of the largest specimen of them 

 the dimensions are given above. The species is named in honor of 

 Mr. J. A. Singley. 

 Pis. splendidulum n. sp. 



Mussel small, well inflated, rather ovoid in outline, scutum and 

 scutellum rather well marked, the former often prominent ; beaks 

 slightly posterior, somewhat prominent, moderately large, rounded ; 

 color pale to deep horn, surface polished, with very fine, somewhat 

 irregular stria?; shell thin, transparent; hinge rather fine but well 

 formed, plate narrow ; cardinal teeth longitudinal, lamellar, the 

 right one rather long, slightly curved, most so at both ends, more 

 or less thickened at the posterior end, and often with a groove ; the 

 two in the valve nearly equal, parallel, little curved, the superior is 

 anterior for about one-third of its length ; lateral teeth compara- 



