m IIN<>< mi 59 



and (M.ncciitfic lines. Central areas having tin- dorsal ridi" 



or only minutely punehired ; the longitudinal riUets of the lateral 



area- extend forward Upon the "pleura" or lidet "| tbc e.-ntral 



areas. Posterior valve elevated, the IMIICTO .slightly posterior, 



elevated. 



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

 Anterior valve having 10, central valves 1, posterior valve ID -lii~. 

 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 (Hernphill ; Rush.) 



Chiton ]>iii-]>iir<i8cens C. B. ADAMS, Proc. Boat. Soc. N. II. ii, p. 

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

 Mils'. 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 I'l, breadth '5 inch. 



This species differs from /. floridanus in having all of the valve- 

 decidedly shorter and broader ; the posterior valve much more 

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

 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 27, breadth 12* mill. ; divergence 120. 



Monterey, California. 



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

 with olive and whitish. The main distinction between this form 



