PALLOCHITON. 257 



This genus closely resembles in sculpture as well as structural 

 characters, Chcetopleura Shuttlew.; (Jiffering only in the posterior 

 position of the mucro and the consequent throwing forward of the 

 tail-valve insertion-teeth, characters of no great importance. The 

 slits correspond in position to nothing in the external sculpture. 

 The girdle is decidedly like Chcetopleura, being very sparsely hairy 

 (or smooth) and lacking all appearance of pores. 



P. LANUGINOSUS Carpenter, n. sp. PI. 56, figs. 1-11. 



Shell oblong or ovate, rather elevated, carinated, the side-slopes 

 nearly straight. Surface lusterless, color very variable ; sometimes 

 dull brown or purplish-brown ; sometimes green along the ridge and 

 purple or lilac dotted with black or olive at the sides ; or having the 

 sides of some valves scarlet or even snow-white. 



The median valves are rather acutely beaked in the young, beaks 

 eroded in old specimens. Lateral areas but little raised, sculptured 

 with gem-like pustules scattered irregularly on a flat (microscopic- 

 ally puncticulate) ground ; the pustules often few, rarely wanting 

 on some valves ; central areas sculptured with many closely beaded 

 longitudinal threads, which converge slightly at the ridge, and 

 diverge toward the outer sides of the valves ; on the second valve 

 they diverge at the ridge. Head valve pustulose like the lateral 

 areas. Tail valve (fig. 11) much depressed, the mucro at the posterior 

 end ; anterior area wide, sculptured like the central areas ; posterior 

 area very narroiv, vertical, sometimes pustulose. 



Interior bluish-white, darker at jugum and posteriorly; rarely 

 flesh or pink tinted. Sutural plates very broad; sinus narrow, 

 deep, angular and notched at the sides. Anterior valve having 8-9, 

 central 1 slit, the teeth long, sharp, a little rugose outside ; posterior 

 valve having 10-11 slits, the teeth chisel-shaped, strongly directed 

 forward, smooth and rather sharp. Eaves of anterior and median 

 valves narrow, of posterior valve wider, solid. 



Girdle rather fleshy, leathery when dried, somewhat encroaching 

 at the sutures, and smooth or clothed with sparse delicate hairlets. 



San Diego, California ; Todos Santos Bay to Pta. Abreojos, Loiver 

 Cal. 



Hemphillia lanuginosa CPR., MS. Pallochiton lanuginosus Cpr., 

 BALL, Proc. U. S. Nat. Mus. 1878, p. 297, pi. 3, fig. 21 (dentition). 

 Chiton (^Pallochiton) lanuginosa (Cpr.) Dall, ORCUTT, Proc. U. S. 

 Nat. Mus. 1885, p. 544. 

 17 



