ON THE PERMIAN CHITONIDiE. 257 



Prof. King's "Monograph of Permian Fossils," 1850.* In 1857 

 Mr. Howse again noticed the occurrence of his specimen in a paper 

 on Permian fossils in the " Annals and Mag. of Nat. Hist."| where 

 he identified with it a fossil found in the Unter Zechstein of 

 Ilmenau, by Baron von Schauroth, and named by him Patella 

 Hollebeni. 



In the early part of 1858 I found my first specimens of this 

 species, which I identified with Cal. antiqua. These specimens 

 resembled the one found by Mr. Howse in marginal imperfection. 

 The latter gentleman, in a revise of his paper, mentioned their 

 discovery, and quoted them as additional proof of the authen- 

 ticity of his species ;f he also took this opportunity of cancel- 

 ling the identification of Schauroth's Patella Hollebeni. A 

 month or two after this I found further specimens, and subse- 

 quently, as already related, I became aware of their true generic 

 relations. In justice to Mr. Howse, it may be added that, on 

 submitting my later acquisitions to his notice, he freely admitted 

 his mistake, and agreed in referring the species to Chitonellus. 



C. antiquus has only occurred in the shell-limestone of Tunstall 

 Hill, in which it is rare. 



2. C. Hancockianus, spec. nov. (PI. XIII., figs. 1-13, including 



spines.) 

 Posterior plate subquadrate, wider than long, pyramidal; 

 apex rather posteriorly situate ; the lateral surfaces slope at a right 

 angle, and the anterior and posterior surfaces at a more acute angle ; 

 the anterior and lateral margins are convex vertically, that of the 

 posterior is arched ; surface coarsely ribbed, four or five ribs occu- 

 pying the anterior, lateral, and posterior slopes respectively ; 

 the anterior and posterior ribs are more prominent than the late- 

 ral ones, but those at the angles are the largest; strong irregu- 

 lar lines of growth mark the general surface; process of insertion 

 extending round the whole of the plate within the outer surface, 

 and at anterior angles produced into bluntly-pointed apophyses, 

 also at the posterior angles rather slightly produced, denticulated 



* Mon. Perm. Foss., Appendix, p. 247. t 2nd ser., vol. ix., p. 464. 



X Trans. Tyneside Nat. Field Club, vol. iii., p. 273. 



