290 CERATOZONA. 



Genus X X VIII. CERATOZONA Dall, 1882. 



Ceratopltnrus ('PR., Table of Regular Chitons, 1873, type C. 

 iiuililinyi Rve. Not of Diesing, 1850. Ceratozona DALL, Proc.U. 

 8, \;it. Mus. 1881, p. 283, 286 (Jan. 20, 1882). Newcombia CPR., 

 V\. type C.setosus Sowb. Not Neivcombia Pfr., Malak. Bl. i, p. 



117. 1854. 



Valves strong, exposed. Insertion plates of anterior valve long, 

 sharp, rugose outside, thickened at the slits, which correspond in 

 position to the external ribs ; median valves with similar propped 

 teeth ; tail valve having the teeth thick, shorter, rugose, sinus 

 solid. Girdle tough, bearing peculiar corneous spines, similar in 

 substance to itself, generally sparsely bunched, at the sutures. The 

 gills extend the entire length of the foot. Type C. guildingi Reeve 

 = C. rugosa Sowb. 



Shuttleworth may readily be excused for grouping the type of this 

 genus in Chcetopleura. Compared with Ch. hennahi it is seen that 

 both have the teeth sharp, and rugose outside ; both have the eaves 

 solid or occasionally with a row of minute pores along the outer 

 bases of the teeth ; and finally both have horny spinelets on the 

 girdle. But in Ceratozona the insertion teeth are thickened at the 

 slits which correspond in position to the riblets of the exterior ; the 

 valves are much more firmly held in the tough girdle, and the 

 appendages of the latter are much more deeply inserted in its sub- 

 stance. If we examine an alcoholic example of Chcetopleura 

 h> n/i'iJti we find that the cuticle of the girdle peels off readily, bringing 

 with it all the spinelets, which leave shallow pits in the fleshy sub- 

 stance of the girdle; but in Ceratozona, only the smaller hairs are 

 thus readily removed, the larger ones being deeply and very 

 intimately attached. Moreover, in most specimens, a pair, or a 

 small bunch of spines, may be detected near each of the sutures ; 

 but this character is often obscure or even wholly obsolete. From 

 Nuttallina this group differs in the solidity of the sinus, the less pos- 

 terior mucro, generally rugose and " propped " teeth, and the 

 peculiar girdle-spines. 



C. RUGOSA Sowerby. PI. 61, figs. 33-37, 41-45. 



Shell oblong, rather convex, the back broadly arched. Surface 

 generally much eroded, green, olive or slate-blackish on the sides, 

 the central areas whitish along the middle, flamed with blackish at 

 the sides, or green there; tail valve having a broad pink ray 

 behind. 



