388 OARBONIFKROUS FORMATIONS AND FAUNAS OF COLORADO. 



"This beiuitiful littlr group includes all thoso spirifei's analogous to tho tS. ijyihri- 

 cata, S. lineafa., S. mivrogemma, S. reticulata^ 6'. rfccMssato, etc., having a reticulated 

 or striated surface combined with the general form and cardinal area of Martinia 

 McCo_v, in M'hich genus I formerly placed them, although they obviously formed a 

 verj' marked group, distinguished bj? its small size, reticulated or striated surface, 

 and very remarkably by the entire absence of the mesial fold in most of the species 

 (in the one or two species which possess a trace of the mesial fold it is ver}^ slightlj' 

 elevated). But the internal structure which I have recently seen in three of the 

 species presents a very distinct and important character; the dental lamellas, instead 

 of converging toward the beak, as in all the other forms of Sjnrifer, are in those 

 perfectly' parallel to each other and to the central septum, in their whole length, 

 thus confirming by a vei'y interesting internal peculiarity the easily recognizable 

 external characters. The genus is Carboniferous and Devonian." 



The term Heticularia seems to have gained but little acceptance, and the species 

 distinguished under it were for the most part merged with the genus Spirifer. 



Waagen, however, in 1887 employed the name in a full generic sense, assigning 

 distinctive characters both externally and internally. The distinctive external char- 

 acters of this group mentioned by this author are the general orbicular shape, short 

 hinge line, and the surface ornamentation, consisting of hollow, double-barreled 

 spines. "Internally," he says, "the ventral valve is without any partition; neither 

 dental plates nor a median septum is present. The muscular impressions are situ- 

 ated in an elongatelj^ oval groove. In the dorsal valve also not a trace of any parti- 

 tions can be found; no septum nor shelly support of the dental sockets has been 

 observed by me. A hinge plate does not exist."" 



In 1892 Hall and Clarke commented upon the term Heticularia as follows, assign- 

 ing to it the same characters as Waagen: * 



" Reticular ia (op. cit., pp. 128, 142). First species cited, Terel)ratula imhricata 

 Sowevhy—A7io?nites liiieatus 'M.?i\'tm = Spirifer lineatu,^ of authors. Shells of this 

 type have the short hinge and the smooth or gently plicated surface characterizing 

 Martinia, and like the latter have neither dental plates nor septa on the interior. 

 The name is based upon a species whose surface is covered with concentric fimbrite 

 of double-barreled spines bearing single rows of lateral spinules, and must probably 

 be restricted to this type of exteiior, as in the more strongly plicated of the fimbri- 

 ated spirifers the surface spines are simple." 



These authors, however, reduce the value of this term^ below that of a subgenus, 

 and employ it as a collateral or synonymic title for the group of spirifers which they 

 call "the dMplicisjnnei.^'' To this group Hall and Clarke refer "/S". fimbriattis Conrad, 

 S. aiihmidifenm Meek and Worthen, of the Hamilton group; S. hirtus White and 

 Whitfield, of the Choteau limestone; S. pseudoUneatus Hall, of the Kinderhook and 

 Keokuk groups; S. setigerus Hall, S. lineatus Martin, and S. jjerplexus McChesney, 



a Mem. Geol. Surv. India, Palseontologia Indica, Salt Range Fossils, vol. 1, 1887, p. 538. 

 i'Pal. New York, vol. 8, pt. 2, 1894, p. 20. 



