OF CONCHOLOGY. 131 



Leptothyra paucicostata, n. S. 



Leptothyra paucicostata, Dall, MSS. I860. 



Shell small, depressed, rounded, of three whorls. Sculpture 

 consisting of seven revolving strong ridges, with the interstices 

 deeply channelled, and marked by evident lines of growth. In 

 a few specimens these are thickened at regular intervals, forming 

 faint transverse riblets, which do not reach as high as, or pass 

 over, the revolving ribs. Suture deep, channelled. Apical 

 whorl smooth, translucent, the others solid and strong. Aper- 

 ture rounded, peristome thickened, continuous with an internal 

 groove for the operculum. Columella ending in a tooth-like 

 knob or callosity, which is especially sharp and prominent in 

 young shells. Throat pearly white. Operculum of few whorls, 

 smooth, externally concave with thickened edges ; circular, cal- 

 careous. Color of shell usually of a rusty brown, on the ribs 

 alternating darker and lighter in spots, or reddish, in a similar 

 way, or pure white. Interspaces usually light, but sometimes 

 of the same color as the ribs. Alt. -12, lat. -2 in. Defl. 100°. 



Habitat, Monterey, dead on beach, ten specimens, Dall, 1866. 

 Catalina Island, Cooper, 60 fathoms. 



This shell is more nearly allied to L. sanguined than to L. 

 vacula, which it more nearly resembles in size. It is uniformly 

 smaller, when mature, than L. sanguined, which has more than 

 twice as many ribs, and an average width of "34 in., with the 

 same number of whorls. It is well distinguished by its few 

 prominent, strong ribs, small size, and usually also by its color, 

 which, even when reddish, is lighter and more broken than in 

 the normal sanguinea. 



FISSURELLIDyE. 



LUCAPINA CRENULATA, Sbv. 



Mantle smooth and black like India-rubber, covering the shell 

 in life, edges rounded, entire, without papillae. Foot smaller, 

 oval, with an impressed median line behind on the lower surface. 

 Muzzle short, rounded-transverse, with an entire edge. Tenta- 

 cles long, pointed, clavate. Eyes on prominent rounded tuber- 

 cles behind the tentacles. A serrated frill passes in the com- 

 missure between the foot and the mantle, from behind one eye 

 tubercle clear around to the same point on the other side. Anus 

 prominent, elevated immediately below the hole in the shell. 

 Gills curled inward at their tips. Jaw in two tridentate pieces ; 



dentition 5o+(^+3-3+>g)+5o' 



Monterey to San Diego, California. 



