Vol. XI] BERRY— FOSSIL CHITOXS 481 



liarly fluted-out interspaces between the latter. On the basis 

 of such insufficient material, however, it is doubtfully advisable 

 to erect a new species. 



Subfamily Callistochitonirue Berry, new subfamily 



Genus Callistochiton Carpenter, 1882 



32. Callistochiton decoratus punctocostatus Pilsbry, 1896 



(Plate XIV, figs. 1-6) 



1893. Callistochiton decoratus Pilsbry, Man. Conch., (1), v. 



15, p. 87, p. 16, f. 54 (not of Carpenter, 1893). 

 1896. Callistochiton decoratus var. punctocostatus Pilsbry, 



Nautilus, v. 10, p. 50. 

 1919. Callistochiton decoratus Chace and Chace, Lorquinia, 



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



Fermi n, Cal.). 

 Diagnosis: Valves of moderate thickness, rather depressed, 

 but carinate; side slopes distinctly arcuate; lateral areas raised, 

 strongly radially bicostate with the central sulcus decussated, 

 the ribs at first tubercular and subcarinate, later smoother and 

 often developing a secondary sulcus on the ridge or even bifur- 

 cating; head valve with 11, posterior area of tail valve with 9 

 similar ribs, their interspaces concentrically decussated ; central 

 areas in adult with perhaps 10-15 longitudinal ribs, nearly 

 equal in width to the interspaces, across which they are con- 

 nected by arcuately-transverse radial threading, the upper- 

 most sculpture usually entirely lost on the jugum, which then 

 shows a triangular smooth area of varying extent; mucro of 

 tail valve low, distinctly postmedian, the posterior slope 

 gradual at first, then suddenly steep ; sutural plates low, arcuate, 

 connected across the squarish sinus by a delicately toothed 

 plate; teeth curved, sharp and distinct, not projecting; eaves 

 thin, solid, overhanging; slits 9 to 11, 1-1, 9 to 12, with distinct 

 pore lines leading into them. 



Recorded Range: 



Pleistocene: Lower San Pedro Series — Chiton Bed, 

 Point Fermin, California (Chace and Chace, !). 



Formation doubtful — Deadman Island, San Pedro, 



California ( !). 



Living: Monterey, California (Williamson), to San 



Diego, California (!). 



