46 
PALEONTOLOGY OF NEW YORK. 
In its superficial ornamentation, species of Cyrtina, like those of Cyrtia, 
conform to a marked degree with that of the associated Spirifers. In the genus 
Spirifer it has been shown that the various modes of surface ornament have 
a more or less definite time-value, and the same fact is, to a certain degree, true 
of Cyrtina. In the fauna of the Niagara group the species C. pyramidalis. Hall, 
has an exterior probably fimbriate like that of Spirifer sulcatus. The greatest 
individual and specific development of these forms is in the Devonian where 
the representatives are mostly coarsely plicate shells with smooth fold and 
sinus, like the prevailing type of Spirifer of the same fauna. Among these are 
C. Dalmani, Hall, of the Lower Helderberg, C. crassa, Hall, of the Corniferous 
limestone, C. Hamiltonensis, Hall, of the Corniferous, Hamilton and Chemung 
groups, C. triquetra, Hall, and C. umbonata. Hall, of the middle Devonian, and 
C. acutirostris, Shumard, of the Choteau limestone. In the Oriskany sandstone 
occurs C. rostrata, Hall, a large species with the exterior coarsely lamellose and 
finely striated radially as in the associated Spirifer raricosta. C. biplicata, Hall, 
of the Schoharie grit and Corniferous limestone is a somewhat variable form 
with smooth exterior, low fold and sinus and obsolete lateral plications. Species 
with plicated fold and sinus are, like the Spirifers, rare in the Devonian, but 
become more frequent in the Carboniferous where the Aperturati predominate. 
In the American Devonian, C. curvilineata, White, is the only form of this 
character, and while this type is wanting in our Carboniferous faunas so far 
as known, it is represented in the European Carboniferous by C. carbonaria, 
McCoy, C. dorsata, McCoy, and C. septosa, Phillips, the last a large, broad¬ 
winged species with the external expression of Syringothyris. In the Waverly 
group of Ohio occurs the C. lachrymosa, sp. nov., a form with faint plications 
and strongly pustulose surface covered, near the beak, by fine concentric lines. 
The cherty beds of the Burlington series in Iowa contain an undescribed 
species which in external aspect is extremely like the Spiriferinas of the 
Keokuk and Chester groups, (e. g., S. subelliptica and S. transversa, McChes- 
ney), having the surface covered with closely crowded, concentric and fimbriated 
lamellae. 
