156 MANUAL OF THE MOLLUSCA. 



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A?iimal with a broad head, destitute of tentacles ; eyes sessile on promi- \ 

 neut rounded lobes ; gill ? siugle. The siphonariee are found between tide- 

 marks, like limpets ; Mr. Gray places them with the pulmonifera, between | 

 auriculidse and cyclostomidse. | 



Distr., 30 sp. Cape, India, Philippines, Australia, New Zealand, Pacific, j 

 Gallapagos, Peru, Cape Horn (Cuming). i 



Fossil, 3 sp. Miocene — . f ^ 



FAMILY XIV., Dentaliad^. Tooth-sheUs. { 



Dentalium, L. 



Type, D. elephantinum. PL XL, fig. 27. 



Shell tubular, symmetrical, cm'ved, open at each end, attenuated pos- , 

 teriorly ; surface smooth or longitudinally striated ; aperture circular, not j 

 constricted.* 



Animal attached to its shell near the posterior, anal orifice ; head rudi- i 

 dimeutary, eyes 0, tentacles ; oral orifice fringed ; foot pointed, conical, \ 

 with symmetrical side- lobes, and an attenuated base, in which is a hoUow ' 

 communicating with the stomach. Branchise 2, symmetrical, posterior to the i 

 heai't ; blood red (Clarke); sexes united? Lingual ribbon wide, ovate;] 

 rachis 1 -toothed ; uucini single, flanked by single u^narmed plates. ; 



The tooth-shells are animal-feeders, devom-ing foramiaifera and minute i 

 bivalves ; they are found on sand, or mud, in which they often bury them- i 

 selves. The British sp. range from 10 — 100 fms. (Forbes.) « 



Distr., 30 sp. W. Indies, Norway, Brit., Medit., India. I 



Fossil, 70 sp. Devonian — . Europe, Chile. •. 



I 



FAMILY XV., ChitOxMD^. i 



Chiton, L, \' 



Etym., chiton, a coat of mail. ' | 



Ex., C. squamosus, spinosus, fascicularis, fasciatus. PI. XL, figs. 28 — 31. \ 

 Shell composed of 8 transverse imbricating plates, lodged in a coriaceous i 

 mantle, which forms an expanded margin round the body. The first seven 

 plates have posterior apices ; the eighth has its apex nearly in front. The 

 six middle plates are each divided by lines of sculptm-ing into a dorsal and 

 two lateral areas. AU are inserted into the mantle of the animal by processes 

 (apophyses) from their front margins. The posterior plate is considered ho- 

 mologous with the limpet-shell, by Mr. Gray ; the other plates appear like 

 portions of its anterior slope, successively detached. The border of the mantle 

 is either bare, or covered with minute plates, hairs, or spines. 



* D. gadus of Montagu is an annelide, belonging to the genus ditrupa. 



