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 pits, 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 rather abrupt, in the right valve 
the anterior much the largest, slightly projecting inward. 
Long. 2°5, alt. 2°3, diam. 1:7 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, seutum 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 striz ; 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- 
