192 EUDOXOCHITON. 



Lateral areas very strongly radiately ribbed and grooved, the pos- 

 terior rib of each valve broad and crenulated, the other ribs unequal, 

 varying in number, usually split toward the outer edge of the shell. 

 Central areas sculptured with numerous strong but smaller riblets, 

 which near the dorsal ridge converge forward, but on the pleura 

 they diverge strongly, End valves having strong radiating ribs, 

 which split toward the periphery. Umbo of posterior valve prom- 

 inent, in front of the middle. 



Interior blue-green ; sutural plates broad ; sinus rather deep and 

 square, finely toothed. Anterior valve having 23-26, central valves 

 2-3, posterior valve 18-20 slits; teeth stout, blunt, finely and 

 strongly pectinated. Eaves coarsely spongy. 



Girdle covered with coarse convex scales, larger toward the 

 periphery. Length 95, breadth 55 mill. 



Galapagos Is. 



Chiton sulcatus WOOD, Gen. Conch., p. 16, t. 3, f. 1. Sows., 

 Conch. Illustr., f. 12. REEVE, Conch. Icon., f. 15. Radsia sulcata 

 CPR., MS. 



This is one of the most strongly sculptured of all Chitons, and is 

 correspondingly easy to recognize. There are usually two slits in 

 each side insertion-plate, but the second valve occasionally has as 

 many as four. 



C. (Radsia) ccerulescens Shuttleworth, Diagn. n. Moll., no. 4, in 

 Bern. Mittheil. 1853, p. 65. No description of this species has been 

 published. It is said to be from California. Possibly founded on a 

 Ch. virgulatus, q. v. 



Genus XIII. EUDOXOCHITON Shuttleworth, 1853. 



Eudoxochiton SHUTTLW., Bern. Mittheil. 1853, p. 67, type A. 

 nobilis GRAY. Acanthopleura sect. * * f, GRAY, P. Z. S. 1847, p. 

 68, non Guilding. Maugeria sect, f, GRAY, Guide, p. 184, 1857. 

 Chcetopleura ADS. et aL, non SHUTTLW. 



Valves entirely exposed, smoothish, lacking eyes ; mucro flat ; the 

 sutural plates broad and connected across the sinus ; insertion-plates 

 of all valves blunt, closely and deeply cleft, the median valves with 

 3 or 4, end valves with many short slits. Girdle leathery, setose. 

 Gills extending the entire length of the foot. 



The valves, when eroded, are seen under the lens to be densely, 

 evenly and regularly punctured all over. The interior is white, and 



