188 
PALAEONTOLOGY OF NEW-YORK. 
son as subgenera : these are Spiriferina, Cyrt^ena and Suessia. Of the 
first and last of these, we have no recognised species in our Devonian 
rocks : the Genus Cyrta;na 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 lamellae; but the wafit of speci¬ 
mens for comparison leaves the question undetermined. 
The Genus Amboccelia was proposed by me in 1360, 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'Coy’s Genus Martinia was proposed for those species 
“ 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 species, 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 he distinguishable from that of other Spirifers. 
“ It will, therefore, be preferable to postpone the adoption of the section Martinia, until some more 
“ tangible differencee can be pointed out” (Introduction, p. 81, 1854). The same opinions are main¬ 
tained by Mr. Davidson in his later publications. 
