26 On the Form, Growth, and Construction of Shells. 



beak, through which is an aperture for the passage of the 

 pedicel, by which the shell is attached to foreign bodies in 

 the sea. 



The ancient Etruscan and Roman lamps have so much the 

 general form of these shells as to have given rise to the name 

 u lamp-shells/'' the beak with its pedicel corresponding to the 

 spout of the lamp through the hole in which the wick passes. 

 On the Coloured Plate (see Vol. x., p. 241, Fig. 11) we figure 

 Waldheimia (Terebratula) Australis, an elegant form, named 

 after the accomplished Russian naturalist, Fischer de Waldheim. 

 The visitor to the shell- gallery of the British Museum may see 

 in the Brachiopod case, a stone dredged up by Professor J. 

 Beete Jukes, in Port Jackson Harbour, Sydney, New South 

 Wales, to which more than thirty specimens of Waldheimia 

 are attached. 



The shell-valves of the Terebratula are articulated together 

 by two curved teeth arising from the border of the ventral, or 

 beaked valve, which fit into two sockets in the other. 



So complete is this hinge that it cannot be separated 

 without injury to the shell ; nor can the valves of Waldheimia 

 be opened more than one-eighth of an inch without applying 

 force. 



If we rupture the hinge of any recent specimen we shall 

 see that the muscles and digestive organs of Terebratula 

 occupy an extremely small space near the beak of the shell, 

 and are partitioned off by a membrane from the general cavity, 

 which is occupied by the fringed arms, that give rise to the 

 name {Brachiopoda), it having been supposed that these 

 organs corresponded with the foot of the Gasteropod. But it 

 seems more correct to consider the pedicel as the true repre- 

 sentative of the molluscan foot. These ciliated arms are 

 variously modified in the different genera. They form two 

 separate spiral coils in Rhynchonella and Lingula, but are 

 united together by a membrane, and are only spiral at their 

 tips, in Terebratula and Discina. 



In Waldheimia, the smaller, or dorsal valve, which is fitted 

 with the hinge-sockets, is also provided with a shelly loop in 

 its interior, for the support of the fringed arms. These fringed 

 arms correspond with the labial tentacles of the ordinary 

 bivalves and the ciliary organs around the mouths of 

 Polypes. 



Pew mollusks present points of greater interest than do 

 the Brachiopoda. They all inhabit the sea ; the fully 

 developed shell being always found attached to rocks, or 

 stones, branches of coral, or to^ other shells. The young 

 (although their development has not as yet been recorded) are 

 doubtless unattached, and able to swim freely, like the fry of 



