CALLISTOCHITON. 263 



lamina deeply slit on each side. Girdle imbricated with striated 

 scales. 



Length Hi, breadth 7J mill. ; divergence 135. (Q)r.) 



Sta. Barbara (Cooper, Cal. State Coll. no. 1077) ; Monterey (Can- 

 field, coll. Cpr.) 



The above description is quoted from Carpenter's MS. He gives 

 the following additional notes : " This species with a general resem- 

 blance to pulchellus, is known outside by its stronger sculpture, flat- 

 tend anterior and tumid posterior valve ; and by its sharp back with 

 flattened sides. It is one of the most remarkable peculiarities of 

 Chitons that they are so particular in special adornment of their tails, 

 while their heads are covered with very uniform plates. In this 

 species this peculiarity culminates. Not only the radiating and fur- 

 belowed arrangement of the teeth presents the greatest differentiation 

 yet observed in a Chiton, but the fluting of each individual finger- 

 like tooth adds special beauty to the complex pattern." 



Figures 7, 8, 13-16 are from drawings prepared for Dr. Carpenter ; 

 fig. 12 represents the tail valve of a typical specimen before me, for 

 comparison with that of the following variety. 



Var. MIRABILIS Pilsbry, n. v. PI. 58, figs. 7, 8, 9, 10, 11. 



Shell oblong, elevated, the back angular, side-slopes convex. 

 Surface lusterless, dull brownish, the lateral areas and end valves 

 blackish. 



Valves not beaked; the lateral areas widely separated by the 

 eroded beaks, greatly elevated, each split by a deep median sulcus, the ' 

 two ribs thus formed bearing coarse transverse grains. Central areas 

 sculptured with about 15 narrow longitudinal cords, parallel at the 

 dorsal ridge except on the second valve in which they diverge forward ; 

 the interstices wider than the cords, and finely latticed across. 

 Anterior valve having 9 stout radiating ribs, strongly granose, and 

 with the exception of the two outer ones, they are generally not bifid. 

 Posterior valve much higher than the anterior, the mucro some what in 

 front of the middle, the area behind it enormously developed, elevated 

 and convex, sculptured with 4, 5 or 6 primary stout ribs, each of 

 which splits into two ; the two outer ribs are broader, and split into 

 several riblets. 



Interior bluish- white ; sutural-laminse slightly connected across 

 the squarish sinus. Anterior valve having 9, central 1, posterior 

 valve 22 slits ; teeth short, somewhat roughened. Eaves broad, 

 calloused. 



