80 



ISCHNOCHITON. 



I. PUSILLUS Sowerby. PI. 8, figs. 69, 70. 



Shell small, obovate, whitish ; back elevated ; intermediate valves 

 narrow, very minutely punctulate ; lateral areas somewhat distinct; 

 posterior valve larger, the apex central, inclined backward. (Soicb.') 



Length 6}, breadth 2 mill. 



Pacasmayo, Peru, on a coral reef in 17 fms., 9 miles from shore. 



C. pusillm Sows., P. Z. S. 1832, p. 57 ; Conch. Illustr. f. 31. 

 REEVE, Conch. Icon. f. 189. 



Carpenter's notes on the two specimens in the Cumingian collec- 

 tion are as follows: Length 5i, breadth 2* mill. ; divergence 90, 

 nearly semicircular. Small, whitish-ashen, long, arched. No 

 jugum or jugal area. Lateral areas slightly swollen ; granulated, 

 but no other pattern. Mucro rather elevated, posterior slope very 

 concave. Posterior valve with 11, median 1, anterior 10 slits. 

 Teeth sharp, long and very thin; eaves conspicuous, not spongy. 

 Sinus deep, broad, flat, not channelled. The shell might pass in 

 sculpture for a young punctulatissimus ; in shape and size for Lep- 

 tochiton cancellatus; but as far as I can see the girdle scales, they 

 are very minute and like Trachydermon, but they have mostly per- 

 ished, and the specimens have been rather smashed and are in bad 

 condition. 



I. RUBER Linne. PL 7, figs, 50-56. 



Shell oblong, elevated, solid, the back roundly subangular, lat- 

 eral slopes somewhat convex; surface apparently smooth except 

 for well-marked grooves or wrinkles, indicating growth-periods. 

 Under the microscope, however, an excessively fine reticulation is 

 visible. The color is light buff, marbled all over with orange-red 

 in various patterns, or entirely suffused with reddish ; usually hav- 

 ing a red dorsal stripe bordered on each side with buff. 



The anterior valve is twice as wide as long, crescentic rather 

 than half-round. The intermediate valves are slightly beaked, 

 their lateral areas slightly raised and having stronger concentric 

 wrinkles than the central areas. Posterior valve having a rather 

 elevated but obtuse median umbo. 



The interior is bright pink. The sutural plates are wide, large ; 

 the jugal sinus is deep, narrow and angular. The insertion plate of 

 the anterior valve has 8 to 11 slits; intermediate valves normally 1 

 slit; posterior valve 7 to 11 slits. The insertion plates are sharp 

 and smooth. 



