38 



154. scabriculus, Soio. 166. 



155. scarabeus, Reeve. 167. 



156. sculptus, Sow. 168. 



157. scutiger, Ad. $- Reeve. 169. 



158. segmentates, Reeve. 170. 



159. setiger, King. 171. 



160. setosus, Sow. 172. 



161. Siculus, Gray. 173. 



162. Sinclairi, id. 174. 



163. Sitkensis, Reeve. 175. 



164. Sowerbyanus. 176. 



165. spiculosa. 177. 



spiniger, Sow. 

 spinosus, Brug. 

 spiuulosus, Sow. 

 squamosus, Linn. 

 Stangeri, Reeve. 

 Stokesii, Brod. 

 striatus, Barnes. 

 striolatus, Gray. 

 Sueziensis, Reeve. 

 sulcatus, Wood. 

 Swainsoui, Sow. 

 textilis, Gray. 



178. truncatus, Sow. 



179. tulipa, Quog. 



180. tunicatus, Wood. 



181. undulatus, Q/iog. 



182. ustulatus, Reeve. 



183. violaceus, Quog. 



184. virescens, Reeve. 



185. virgatus, irf. 



186. virgulatus, &>«<?. 



187. vol vox, Reeve. 



188. Watsoni, Sow. 



189. Zelandicus, Qwoy. 



fflgure. 



Chiton spiniger. PI. 25. Fig. 147. Shell, showing the eight valves 

 in a broad cartilaginous frame beset with calcareous bristles. 



Genus 2. CHITONELLUS. 



Animal ; similar to that of Chiton. 



Shell ; of eight isolated pieces, longitudinally oblong valves, of 

 which the apophyses are much produced, partially imbedded in 

 the substance of the mantle, which is thick and elongated ; valves 

 approximating towards the head. 



The Chitonelli resemble the Chitons in their internal organization, but 

 in connection with a difference in the condition of the mantle and its shell, 

 there is a marked difference in their habits and geographical distribution. 

 The mantle is very thick and fleshy, peculiarly elongated, sometimes covered 

 with a harsh down, but mostly tough and leathery ; it is invariably desti- 

 tute of any horny, cartilaginous part, and is never furnished with spines, 

 bristles, or any sort of calcareous armature. The valves of the shell are of a 

 longitudinally oblong form, with the inner posteriorly projecting plates or 

 apophyses very much produced and firmly imbedded in the substance of 

 the mantle. Sustained by the apophyses alone, the valves are perfectly 

 isolated from one another, far removed, in the more typical species, pos- 

 teriorly, but approximating towards the head, where they are sometimes 

 much worn by the friction arising from the animal's propensity of thrust- 

 ing itself into holes and crevices of rocks. 



The Chitonelli are not found in company with Chitons. On the south- 



