FISHES OF THE CARBONIFEROUS SYSTEM. 119 
this continent. It can be readily distinguished from all the species described 
abroad by the small number of its radiating ridges. This specimen is from 
the Catskill group of Tioga County, Pa., and was discovered by Mr. Andrew 
Sherwood, to whom I am indebted for an opportunity of examining it. 
Since the discovery of the tooth of Dipterus Sherwoodi many others 
belonging to the same genus have been obtained from the Chemung rocks 
and are noticed in this paper, but they are distinguishable at a glance from 
this by their greater number of radiating ridges and smooth or less distinetly 
tuberculated triturating surfaces. The type specimen of this species is in 
the cabinet of the School of Mines, Columbia College. 
Dipterus (CTENODUS) RADIATUS, N. sp. 
Plate XXVII, Fig. 33. 
Another tooth belonging to the genus Dipterus has recently been sent 
to me by Mr. Sherwood. He obtained it from the same formation and 
locality as that which many years ago furnished the type specimen of D. 
Sherwoodi. 
The new tooth is, however, quite distinct specifically from that, viz, it 
is much smaller, being only half an inch long, and has three strong and two 
faintly defined, widely divergent, curved, obscurely tuberculated ridges on the 
crown surzace. 
It is apparently undescribed, and I would propose for it the name of 
Dipterus (Ctenodus) radiatus, as expressing one of its most striking characters, 
the great divergence of the ridges as they leave their common starting-point 
in the center of the interior edge of the crown. A more detailed description 
can only be given when other specimens shall be obtained. 
GYRACANTHUS SHERWOODI, 0. sp. 
Plate XVIII, Figs. 4-4”. 
Spines four to six inches in length by half an inch in width, unsym- 
metrical, obliquely rounded or spatulate at the base, gently curved and acute 
at summit, much compressed laterally ; central cavity reaching nearly to 
point, opening posteriorly only near the base; sides bearing numerous 
rominent, oblique, acute, beaded, parallel ridges. 
3 p] ’ ? i oD 
