[ 62 J 



many genera, as Terebratula and Rhyiichonella, had a prominent beak 

 with a circular or otherwise shaped perforation or foramen at, or 

 near, its extremity, partly completed by one or two plates termed a 

 deltidiam ; through the foramen passed a bundle of muscular fibres 

 termed a peduncle, and by which the animal was, in many species, 

 attached to sub-marine objects during at least a portion of its 

 existence. It was, however, certain, fi'om the admirable researches 

 of Professor Morse, that the embroyo of some, if not of every 

 species, swan most actively in every direction and turned abruptly 

 about; but that, in the fourth stage of its development, it became 

 attached, the peduncle widening at its end into a sucking disk. 

 Other species showed no indication of ever having been attached, 

 while some, that had been fixed by means of a peduncle during a 

 part of their existence became attached at a more advanced stage 

 of life, the opening for the peduncle becoming gradually cicatrized. 

 Lastly, certain forms appeai'ed to have adhered to submarine 

 objects by a lai'ger or smaller portion of the surface of their ventral 

 valve, or by spines (Stropludosia) during their entire life. In 

 external shape the valves were essentially symmetrical, which was 

 not the case with the Lamellibranchiata, so much so, that certain 

 Brachiopod shells received the name of Lampides from some early 

 naturalists, but while such might bear an obscure kind of 

 resemblance to an antique Etx'uscan lamp, by far the larger number 

 in no way i-esembled one. The valves were also either articulated 

 by means of two curved teeth developed from the margin of the 

 larger valve and fitting into sockets in the corresponding part of 

 the smaller one, or they were unarticulated and kept in place or in 

 juxtaposition by the means of muscles especially provided for that 

 purpose. 



SHELL STEUCTURE. 



The structure of the shell had been shown by Dr Carpenter, 

 Professor King, and others to be generally distinct from that 

 of the Lamellibranchiata or Gasteropoda. In some families, 

 according to Professor King, it consisted of three divisions, 

 the innermost and middle divisions, which constitute the entire 

 thickness of the valve, were calcareous, with a prismatic or fibrous 

 structure ; while the outer division consisted of a very thin 

 membi-ane. The innermost and intermediate divisions in some 

 families were traversed by minute tubular canals, which passed 



