CALLISTOCHITON. 273 



with two very large, prominent ribs ; median areas wide and 

 punctate. Girdle minutely scaly. Length 7 mill. ( Orb.} 



Arica, under stones at low water. 



" Allied to C. pulchellus of Gray, differing in the granulous and 

 scaly, not smooth, girdle, by the two ribs of the lateral areas instead 

 of three, and by the punctate central areas, which in the other 

 species are striated." (Orb.~) 



It must be remembered that the " C. pulchellus of Gray " alluded 

 to by Orbigny, is not the true pulchellus of Gray, but some totally 

 different species of Chcetopleura or of Tonicia. 



C. SHUTTLEWORTHIANUS Pilsbry, n. sp. PL 21, figs. 42, 43, 44, 45, 



46. 



Shell oval, depressed but dorsally carinated, the side-slopes nearly 

 straight; lateral areas strongly raised, bicostate, the ribs nodose; 

 central areas having a coarse raised net-work in the middle, and 

 longitudinally ribbed toward the sides. Girdle broad. Color of 

 both shell and girdle intense orange yellow. 



The lateral areas bear two strong ribs which bear stout transverse 

 tubercles, the intervening spaces being closely granulate. The central 

 areas have coarse net-like sculpture (fig. 45), which becomes much 

 finer toward the beaks, and is transformed into a longitudinal cos- 

 tulation at the sides. The front valve has 16 or 17 strong, tuberculate 

 radiating ribs, the whole covered by a fine granulation. The poste- 

 rior valve is depressed, having a rather low but acute and slightly pos- 

 terior mucro, the slope back of it being concave. It is sculptured 

 similar to the head-valve, except that the concentric sculpture pre- 

 dominates over the radiating. 



The interior is flesh-colored ; anterior valve with 10, central 1 

 slit ; sutural plates low and rounded ; sinus shallow, flat. 



Girdle wide, compact, very densely clothed with closely imbricat- 

 ing scales, the terminations of which are not striated, although the 

 basal portions are distinctly grooved (pi. 21, fig. 46.) 



Length 14, breadth 9 mill. 



Key West, Florida (Henry Hemphill.) 



This handsome species constitutes one of the links between Callis- 

 tochiton and Ischnochiton, agreeing in the teeth with the latter genus. 

 The sculpture, however, is much more like Callistochiton pulchellus 

 than like any Ischnochiton known to me ; but, on the other hand, 

 the profile of the tail-valve differs utterly from that West Coast 

 species. 



18 



