CHITON. 153 



ee. Lateral areas with 2-3, pleura 14 riblets, muricatus. 

 aa. Central areas smooth, lacking longitudinal ribs. 

 b. End valves granose-lirate or pustulose. 



c. Front of diagonal line obviously wrinkled or pitted. 



d. Shell and girdle uniform dark green, rusticus. 



dd. Shell variegated, girdle-scales striated, sinclairi. 



ddd. Shell or girdle varied, scales smooth, viridis. 



cc. Front of diagonal line smooth. 



d. Pustules scattered ; shell and girdle uniform blackish, 



marquesanus. 



dd. Finely beaded ; shell and girdle banded, squamosus. 



bb. End valves finely striated. 



c. Shell oblong, divergence about 110. subfuscus. 



cc. Shell elongated ; divergence about 98. bowenii. 



AA. LATERAL AREAS SMOOTH OR CONCENTRICALLY SCULPTURED. 



a. Whole surface smooth. 

 6. Mucro near the anterior margin. 



c. Color black and olive-yellow, with snowy lines, albolineatus. 

 cc. Purple or olive mottled. 



d. Sutural-plates within dark-blotched at base ; sinus nar- 

 row, Icevigatus. 

 dd. Sutural-plates within not blotched ; sinus wide, 



marmoratus. 



bb. Mucro central, tulipa. 



aa. Central areas longitudinally sculptured, (species not tabulated.) 



West Indian species. 



Mainly large forms, with smooth scales and notably anterior 

 mucro. They are closely allied to the species of the Panamic 

 region. 



C. TUBERCULATUS Linne. PI. 33, figs. 58, 59, 60. 



Shell oval-oblong, rather elevated, carinated, the side-slopes nearly 

 straight. Color varying from light olive to dark green or dark 

 olive-brown, unicolored sometimes, but generally speckled on the 

 side-areas and end-valves, often clouded on the central areas; some 

 of the valves having a dark stripe on the ridge. 



Lateral areas raised, sculptured with about 5 cord-like radiating 

 riblets, which are sometimes subcontinuous, but usually are much 



