282 MANUAL OF THE MOLLUSCA. 



deep siphonal groove, which produces a slight projection on the 

 margin. 



Animal with a broad head, destitute of tentacles ; eyes sessile 

 on prominent rounded lobes ; gill ? single. The siphonariae 

 are found between tide-marks, like limpets ; Dr. Gray places 

 them with the pulmonifera, between the auriculidae and cyclos- 

 tomidse. 



Distribution, 41 species. Cape, India, Philippines, Australia, 

 New Zealand, Pacitic, Gallapagos, Peru, Cape Horn. (Cuming.) 



Fossil, 3 species. Miocene — . France. 



Family XIV. — Dentaxiad^. Tooth-shells. 

 Dentalium, L. 



Type, D. elephantinum. PL XI., Fig. 27. 



Shell tubular, symmetrical, curved, open at each end, 

 attenuated posteriorly; surface smooth or longitudinally 

 striated ; aperture circular, not constricted.* 



Animal attached to its shell near the posterior anal orifice ; 

 head rudimentary, eyes 0, tentacles ; oral orifice fringed ; 

 foot pointed, conical, with symmetrical side-lobes, and an 

 attenuated base, in which is a hollow communicating with the 

 stomach. Branchise 2, symmetrical, posterior to the heart ; 

 blood red (Clarke) ; sexes united ? Lingual ribbon wide, 

 ovate; rachis 1 -toothed; uncini single, flanked by single 

 unarmed plates. 



The tooth-shells are animal-feeders, devouring foraminifera 

 and minute bivalves ; they are found on sand, or mud, in which 

 they often bury themselves. The British species range from 10 

 — 100 fathoms. (Forbes.) 



Distribution, 50 species. "West Indies, Norway, Britain, 

 Mediterranean, India. 



Fossil, 125 species. Devonian — . Europe, Chili. 



Family XV. — Chitonidje. 

 I Chiton, L. 



Etymology, chiton, a coat of mail. 



Examples, 0. squamosus, spinosus, fascicularis, fasciatus. PI. 

 XI., Figs. 28—31. 



* D. (jadus of Montagu is an annelid, belonging to the genus ditrupa. 



