British conchology : or, an account of the Mollusca which now inhabit the British Isles and the surrounding seas . e tide falls only a few feet; I have taken the samespecies by dredging at various depths from 3 to 90fathoms; MfAndrew and Barrett obtained T. craniumalive at 160 fathoms; and Dr. Wallich has shown mea shell of the last-named species which was broughtup by sounding off the east coast of Greenland in 228fathoms. The nature of the sea-bottom, more than thedepth of water, determines the limit of their habitability. This class has two great and distinct types of form,viz. the jointed
British conchology : or, an account of the Mollusca which now inhabit the British Isles and the surrounding seas . e tide falls only a few feet; I have taken the samespecies by dredging at various depths from 3 to 90fathoms; MfAndrew and Barrett obtained T. craniumalive at 160 fathoms; and Dr. Wallich has shown mea shell of the last-named species which was broughtup by sounding off the east coast of Greenland in 228fathoms. The nature of the sea-bottom, more than thedepth of water, determines the limit of their habitability. This class has two great and distinct types of form,viz. the jointed and hingeless, although a fossil genus(Davidsonia) is considered by M. Bouchard-Chantereauxto form a connecting link between them. The abovedistinction was first noticed and proposed by M. Des-hayes, and it is founded on malacological as well asconchological characters. By far the greater part ofthe Brachiopoda (including the Terebratulidce) belongto the former section, while the other comprises onlyCrania, Lingula, and a few more genera. Both ofthese types or sections are represented in the Britishfauna. 5 i. B O 10 TEREBRATULIDjE. * Jointed. Family I. , Gray. Body oval: arms folded back, and supported either by shellyprocesses issuing from the hinge of the lower valve, or by lon-gitudinal septa or partywalls in that valve : attachment formedby a peduncle, which passes through a hole in the upper valve. Shell longitudinally or transversely oval, more or less con-vex : skeleton or apophysary system consisting of riband-shapedplates, which are frequently looped or united : hinge formed oftwo side-teeth in the upper valve, which lock into sockets inthe lower valve : muscular scars slight and seldom visible. This family is very numerous and diversified in cha-racter, and it is also widely dispersed both in space andtime. Some of its members occur in every sea, fromthe arctic to the antarctic pole; and its geologicalrange appears to include all the known strata, from
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