ISCHNOCHITON. 59 



and concentric lines. Central areas having the dorsal ridge smooth 

 or only minutely punctured ; the longitudinal riblets of the lateral 

 areas extend forward upon the "pleura" or sides of the central 

 areas. Posterior valve elevated, the mucro slightly posterior, 

 elevated. 



Interior white or stained ; sutural plates short ; sinus wide, flat. 

 Anterior valve having 10, central valves 1, posterior valve 10 slits. 

 Teeth sharp, smooth. Eaves narrow. 



Girdle rather wide, alternately bluish and buff, densely clothed 

 with minute, solid, striated scales. Length 16, breadth 7 mill. 



Jamaica (Adams) ; Key West, Florida (Hemphill ; Rush.) 



Chiton purpurascens C. B. ADAMS, Proc. Bost. Soc. N. H. ii, p. 

 9,1845. Ischnochiton purpurascens Ad., DALL, Bull. U. S. Nat. 

 Mus. No. 37, p. 172. 



Adams' description is as follows : Shell much elongated, purplish- 

 ruddy, concentrically striated ; margin wide, very minutely scaly, 

 bluish, alternately paler. Length 1-1, breadth '5 inch. 



This species differs from I. floridanus in having all of the valves 

 decidedly shorter and broader ; the posterior valve much more 

 elevated, the jugum almost smooth. It differs from /. limaciformis 

 in having the lateral areas and end valves conspicuously granulose, 

 etc. 



In this species the valves are almost as short as in the typical 

 Ischnochitons, but the sculpture is quite that of Stenoplax. The 

 mucro is more raised than in any other described Stenoplax. The 

 species is abundant at Key West. 



The color-pattern is excessively variable. 



I. FALLAX Carpenter, n. sp. PI. 16, figs. 17, 18. 



Almost exactly like Ischnochiton magdalenensis in form and sculp- 

 ture, but more roseate ; the central areas pitted ; lateral areas 

 having close radiating wrinkles interrupted by lines of growth. 

 Interior : Posterior valves having 9, central 1, anterior 10 slits ; 

 teeth acute ; eaves conspicuous ; sinus moderate, scarcely laminate, 

 but the jugal part of the valves produced forward. Girdle having 

 very minute granules. 



Length 271, breadth 12J mill. ; divergence 120. 



Monterey, California. 



The color is either entirely reddish-fleshy or clouded and dotted 

 with olive and whitish. The main distinction between this form 



