58 ISCHNOCHITON. 



The characteristic mark of this species is the sculpture of the 

 lateral areas and end valves, which are non-granulated but have 

 slightly serrated concentric flat riblets. The girdle scales are flat, 

 solid, not striated or very obsoletely so, and far more minute than 

 in /. alatus. 



I. FLORIDANUS Pilsbry, n. sp. PI. 17, figs. 19-22. 



Shell elongated, narrow, elevated, the valves roundly arched, not 

 carinated. Color whitish or delicate green, variously marked and 

 mottled with olive, blackish-olive or gray. 



The lateral areas are raised, longitudinally costulate, the riblets 

 cut into granules by radiating impressed or incised lines devel- 

 oped over the whole area or over the forward half of it. End valves 

 similarly cut into granules by radiating and concentric lines. Cen- 

 tral areas covered with longitudinal riblets which are finer and 

 closer upon the jugum, usually showing a tendency to be a little 

 irregular on either side of it, and are granulous toward the outer 

 angles of the areas. Posterior valve large, rather depressed, the 

 mucro slightly posterior. 



Interior pink, blue and white, in various proportions, rarely all 

 roseate or all white. Sutural plates strongly developed, rounded ; 

 sinus wide, deep, square. Anterior valve having 9, central valves 

 1, posterior 9 slits; teeth sharp, smooth or very obsoletely lobed. 

 Eaves narrow, solid. 



Girdle delicately marbled with bluish and gray, densely clothed 

 with rounded, solid, delicately striated scales. 



Length 41, breadth 15 mill. 



Length 35, breadth 11J mill. 



Key West, Florida. (Hemphill.) 



This species is allied to /. limaciformis, differing in the differently 

 sculptured lateral areas. It is also related to C. purpurascens C. 

 B. Ad., but differs in several respects, notably in the flatter poste- 

 rior valve and longer central valves. 



I. PURPURASCENS C. B. Adams. PI. 17, figs. 23, 24. 



Shell elongated, narrow, much elevated, the lateral slopes of the 

 valves nearly straight, dorsal ridge roundly subangular. Generally 

 pale buff, marbled with olive or mottled with black, and having red 

 patches along the dorsal ridge. The lateral areas are raised and 

 longitudinally ribbed, the riblets cut into granules by radiating 

 impressed lines ; end valves cut into coarse granules by radiating 



