3W ZOOLOGY 



long axis of the larva, becoming the body of the future animal ; 

 the larval tentacles and pre-oral lobe become thrown off, and the 

 lophophore is developed. 



CLASS III.— BRACHIOPODA. 



The Brachiopoda are the fabricators of the well-known " Lamp- 

 shells " found in most parts of the world. They occur in the sea 

 at various depths, and were formerly classed under the Mollusca, 

 their characteristic bivalved shell being compared with that of 

 oysters, mussels, &c. 



1. ExAJiPLE OF THE Class — Magellcmia (Waldheimia) lenticularis 



or M. flavcscens. 



Magellania lenticularis is found in great mimbers, at moderate 

 depths, off the coast of New Zealand. An allied species, M. flavcscens, 

 is equally common in the Australian seas, and several other species 

 are known in various parts of the world. 



The body is entirely covered by a shell (Fig. 289) of oval form 

 and pink colour, composed of two pieces or valves, one of which, dis- 

 tinguished as the ventral valve {v. v), projects beyond the other 

 or dorsal valve (d. v), in the form of a short conical hcak (b) perfor- 

 ated at the end by an aperture, the foro.men (b), through which 

 passes a dark brown stalk or peduncle (Fig. 290, B, pd) of horny 

 consistency. In the natural state the peduncle is attached to a 

 rock or other support, and the animal lies with the ventral valve 

 uppermost and with the valves gaping slightly. The pointed or 

 peduncular end of the shell is considered to be posterior in posi- 

 tion, the opposite end or gape anterior. 



It will be convenient to consider the shell first. Both valves are 

 deeply concavo-convex, of a pinkish colour outside, white within. 

 The ventral valve (Fig. 289), as already stated, is produced poste- 

 riorly into a beak {h), terminating in a foramen (/) for the peduncle. 

 The distal margin of the foramen is left incomplete by the shell 

 proper, but is closed by a small double plate, the deltidium (d). 

 Immediately anterior to the beak is the curved hinge-line along 

 which the valve articulates with its fellow, and just anterior to 

 the hinge-line the inner surface of the shell is produced into a pair 

 of massive, irregular hinge-teeth (t). On the inner surface of the 

 valve, towards its posterior end, are certain shallow depressions 

 marking the attachments of muscles (ad. m, d. m). 



The dorsal valve (D) has no beak, but its posterior edge forms 

 a hinge-line which is produced in the middle into a strong cardinal 

 process (c. p) with a curiously folded surface : when the two valves 

 are in position this process fits between the hinge-teeth of the 



