38 PROCEEDINGS OF THE ACADEMY OF [Feb., 



growth, so that at the larger end there are 27 cords in all. The 

 growth-lines are inconspicuous. The shell is broken more or less at 

 both ends. 



Length 19.4 mm.; antero-posterior diameter at larger end 3.7; 

 lateral diameter 3.9 mm.; lateral diameter at smaller end 2.4 mm. 



Pitar (Hysteroconcha) casta n. sp. PL 6, fig. 4. 



The shell is oblong with small, rather plump beaks. Sculpture 

 of continuous, smooth concentric ridges, their edges overhanging the 

 succeeding intervals a little, and some of them broadened into 

 lamellae at the anterior end. They are not enlarged or interrupted 

 posteriorly, and there are no spines. Between the concentric ridges 

 there are fine growth-lines, some of them larger, thread-like. Lunule 

 defined by a groove, radially striate. Interior not seen. Length 

 about 26 mm.; height 19 mm.; semidiameter 6 mm. 



The sole specimen is partially imbedded in material too hard to 

 be removed, so that the internal characters and posterior end could 

 not be examined. The sculjiture, however, is very perfectly pre- 

 served and characteristic, and leaves very little doubt that the shell 

 is related to the recent P. dione (L.). The absence of spines would 

 be expected in an early member of the group. The concentric 

 lamellae are developed less than in P. dione, and turn downwards at 

 the edge. In contour P. casta stands nearer to P. lupanaria. 



Yoldia pisciformis n. sp. PI. 6, fig. 3. 



The shell is much lengthened, the posterior part decidedly atten- 

 uated (end broken), anterior end rounded. Surface nearly smooth, 

 but under a lens showing delicate, rather close grooves in harmony 

 with growth-lines, from the middle downward. A pair of extremely 

 low ribs run in a low curve from the beaks to the anterior-basal 

 margin. The teeth are very numerous, and appear to be about 

 equally so before and behind the beaks. 



Length, as broken, 50 mm.; height 22.6 mm.; diameter 10.8 mm. 



This is much broader than Y. limatula Say, with a sinuation in the 

 basal margin and various other differences. 



A small, very finely grooved Leda is represented by one broken 

 specimen. 



Area consobrina Sowerby. 



Glycymeris tumefactus n. sp. PI. 6, fig. 7. 



The shell is slightly inequilateral, very obese, with rather prominent 

 beaks. Sculpture of many (about 55) extremely low radial ribs, 

 somewhat wider than their intervals, and weak, coarse growth-lines. 



