16 PALAEONTOLOGY OF THE UPPER MISSOURI. 



MOLLUSCA. 



CLASS BRACHIOPODA. 



FAMILY SPLRIFERID^E. 



Shell free, inequivalve, varying greatly in form and ornamentation 

 according to the genera and species ; with or without a cardinal area ; 

 oral appendages large, provided with calcified, ribbon-shaped supports, 

 which are spirally coiled so as to form two cones^ the apices of which 

 are directed outwards towards the lateral margins of the valves. Shell 

 structure fibrous only, or fibro-punctate. 



Animal unknown, apparently sometimes attached by a muscular 

 peduncle. 



Paleontologists generally place in this family all the Brachiopods known to 

 possess calcified spiral oral appendages, however these appendages may be arranged 

 or attached. We agree with Mr. Woodward and some others, however, in sepa- 

 rating from it the genus Atrypa, which differs from the other genera usually placed 

 in this family, in having the cones formed by its spiral oral appendages placed with 

 their apices directed vertically instead of laterally, thus apparently indicating 

 affinities to the Rhynchonellidce (probably also including Stenocisma 1 and Oceloepira), 

 in which the fleshy oral arms are similarly arranged. 



The great differences of form and other characters presented by the other genera 

 usually embraced in this family, render it also highly probable that they belong to 

 more than one family ; but as we can scarcely ever hope to know enough of the 

 affinities of these extinct genera to successfully separate them, it is not probable 

 that any attempt of that kind would meet with much favor. The entire family is, 

 so far as known, extinct, and none of the genera appear to range above the Lias. 



The groups falling within this family, as here defined, are Trigonotreta, Martinia, 

 Spirifina, Spirifer, Syrimgoihyrie, Cyrtina, Suessia, Trematospira, Sjnrigera, Merista, 

 Pentagonia, 2 Nudeospira, Uncites, Retzia, Rhynchospira, Acambonia, &c. 



1 In the Fifteenth Report Regents University of N. Y., 1862, p. 154-5, Prof. Hall proposes the 

 name Zygospira for a genus of which Producta modesta, Say, is the type. It seems, however, that 

 Mr. Conrad had suggested for this shell the generic name Stenocisma; which Prof. Hall proposed in the 

 first Vol. Pal. N. Y. (1847, p. 142) to adopt, should this type prove to belong to a distinct genus. As 

 there was, therefore, no necessity for a new name, Stenocisma will have to take precedence over Zygospira. 



* The name Pentagonia was proposed by Cozzens, in 1846 (Ann. Lye. N. Hist., N Y., IV, p. 158), 

 for a genus, or subgenus of peculiar angular Meristoid shells, of which Pentagonia unisulcata 

 (= Atrypa unisulcata, Conrad, = Pentagonia Persii, Cozzens, = Meristella (Gonioccelia) unisulcata, 

 Hall) is the type. In 1861, Prof. Hall suggests the name Gonioccelia for the same type (Fourteenth 

 Rept. Regents University of N. Y., p. 101). Cozzens' name having priority, however, must be adopted 

 for the group, whether we consider it a genus or a subgenus. 



