188 PALEONTOLOGY OF NEW- YORK. 



SON as subgenera : these are Spiriferina, Cyrt>«;na and Suessia. Of the 

 first and last of these, we have no recognised species in our Devonian 

 rocks : the Genus Cvrt^ena is recognised in two or more species. 



The Genus or Subgenus Martinia was proposed by ,Prof. M'Coy to 

 include species of the type of Spirifera decora, S. elliptica, S. glabra, and 

 others of similar form, having a short hinge-line and rounded cardinal 

 extremities.* In the interior of some species of this type, I have recog- 

 nized some peculiarities in the dental lamellie ; but the want of speci- 

 mens for comparison leaves the question undetermined. 



The Genus Amboccelia was proposed by me in 1860, for certain forms 

 having one valve flat or concave, and the other extremely convex. There 

 appear to me to be, in the typical species, some peculiarities in the mus- 

 cular impressions, which I regard as of importance. The fibrous texture 

 of the shell exhibits some peculiarities ; but I find, that in this respect, 

 it corresponds with a small doubly convex form resembling S. lineata from 

 the Hamilton group. These forms will be noticed more at length after 

 the descriptions of Spirifera proper. 



The following species are arranged upon the plates, as nearly as prac- 

 ticable, in their geological order ; beginning with those of the Schoharie 

 grit, and ending with those of the Chemung group. Since many of the 

 species are common to the Schoharie grit and Corniferous limestone, and 

 few of the species pass into the succeeding formations, I shall follow the 

 apparent natural or chronological order in describing them. 



•Mr. Davidson remarks, that "Prof. M'Cot's Genus Martinia was proposed for those siKJcies 

 " in which the hinge-line was shorter than the width of the shell, and dorsal edges of the cardinal area 

 "obtusely rounded with a smooth surface, and small spiral appendages; but the length of the hinge- 

 " line is so very variable, even in specimens of the same sjxjcies, that on such a character it 

 " seems very unsafe to found a genus. The species are also both smooth and plicated, and the 

 " disposition of the spiral appendages does not appear to be distinguishable from that of other Spirifers. 

 " It will, therefore, be preferable to postpone the adoption of the section Martinia, until some more 

 " tangible diiferencee can be pointed out" (Introduction, p. 81, 1854). The same opinions arc main- 

 tained by Mr. Davidsox in his later publications. 



