CLASSIFICATION OF THE BRACHIOPODA. 101 



Family— STROPHOMENID^. 



Animal unknown, some of the group appear to have Hved free ; others were fixed 

 during the whole or a portion of their existence by means of a muscular pedicle ; no calcified 

 supports for the arms, which were no doubt fleshy and spirally coiled; shell with a 

 straight hinge line, and a low triangular area in each valve ; valves both convex, or 

 with the dorsal or ventral one concave or convex ; shell structure fibrous or punctated. 



Obs. Much difference of opinion has been expressed as to what genera the present 

 family should include, as well as to the name it should retain. Some authors, 

 M. d'Orbigny, Professor M'Coy, &c. prefer that of Orthisidce, (properly Orthida) while 

 others, such as Professor King, advocate Slrophotnenida. I have admitted this last deno- 

 mination more on account of its priority, than on any other consideration. As to the 

 subdivision of the group, we have considered, that in the present state of our knowledge, 

 it would be preferable to restrict the number of genera to four, viz., Orthis, Orthisina, 

 Strophomena, and Leptcena. Professors M'Coy and King have admitted within its limits 

 Chonetes, a genus, as I hope to prove, more nearly related to the Productida, and I am 

 happy to be able to state, that the last-named author has expressed approval of my 

 conclusions. Poramboniies has likewise by some been placed in the present family ; and 

 although I am not prepared positively to deny such a view, I would defer its admission 

 until more is known regarding its internal organisation. M. d'Orbigny is decidedly in 

 error when placing Leptcena in one family, and Strophomena in another. 



This is one of the oldest families, having originated in the lower Silurian epoch, and 

 continued to exist to the end of the Liasic period, where hitherto the latest representatives 

 have been found. 



Genus— Ov.Tiw's,, Balman, 1827. 



Type—0. CALLiGRAMMA or 0. ELEGANTULA, BaJ} Int., PI. VII, figs. 127 — 135, and PL VIII, figs. 136—148. 



Hysterolitiius, of Worm, 1655; o? Linnceus, 1753. 



Anomia (part), of Linnceus. 



Orthis, of Dalman, and the generality of Authors. 



Spirifer of some Authors. 



Terebratula (part), of Beshayes. 



^ Dalman' s first mentioned example is the O. zonula, which he figures with an open fissure. M. de 

 Verneuil refers this species to O. ascendens. Pander ; but in this last, the fissure is entirely covered by 

 a deltidium, and does not agree in this respect with Dalman 's figure. O. eallactis or O. calUgramma may 

 be considered types. 



