450 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



Family Ischnochitonidae 



Subfamily Chaetopleurinae 



Genus Chaetopleura Shuttleworth, 1853 



Subgenus Pallochiton Dall, 1879 



20. Chaetopleura (Pallochiton) gemma Carpenter, 1879 

 (Plate VIII, figs. 10-12.) 



1879. Chceto pleura gemma Carpenter, in Dall, Proc. U. S. Nat. 



Mus., v. 1, p. 296, pi. 1, f. 9 (radula). 

 1892. Chaetopleura gemmea Pilsbry, Man. Conch., (1), v. 14, 



p. 31, pi. 13, f. 69-74. 

 1919. Chaetopleura gemma Chace and Chace, Lorquinia, v. 2, 



p. 42 [2] (recorded from Pleistocene of Pt. Fermin, 



California). 



Diagnosis" ": Valves small, elevated, of moderate thickness, 

 the median ones but weakly beaked, yet leaning strongly back- 

 ward; lateral areas elevated, ornamented with 5-8 radiating 

 series of small, strong, closely placed, projecting, cylindrical 

 pustules, fewer in young shells ; head valve similarly sculptured 

 with very numerous (25-35) series of pustules, usually abraded 

 toward the apex; central areas with 12-18 narrow, rather ir- 

 regularly beaded, longitudinal lirse; tail valve with slightly 

 raised, posterior mucro, the posterior slope steeply terraced and 

 irregularly tubercled ; sutural laminae short; sinus wide, rather 

 deep and angular; tegmentum projecting over and under ar- 

 ticulamentum at suture, especially toward middle of median 

 valves, where such inner surface is even more or less pustulose : 

 teeth short and robust, slightly projecting; eaves roughened, 

 but apparently not spongy; slits 9 to 12, 1-1, 7 to 8. 



Recorded Range: 



Pleistocene: Lower San Pedro Series — Chiton Bed, Point 

 Fermin, California (Chace and Chace, !). 



Living: Straits of Georgia, British Columbia ( !), to Ce- 

 dros Island, Lower California (Lowe) ; between tides to 15 

 fathoms. 



14 Description drawn in part from recent specimens. 



