Description of new North American Trilobites. 335 
The buckler is the only part of this very singular trilobite, which 
has yet been discovered. Ihave therefore more hesitation in deci- 
ding whether it be a Calymene or not. It has been suggested, that 
the extremity of the tail is furnished with an organization similar 
to the ornament on the edge of the front, and that a portion of the 
ornamented edge in that part is produced by the position of the ani- 
mal; it being coiled or rolled up so as to bring the edges of the buck- 
ler and tail together. If this should turn out to be the fact, this tri- 
lobite cannot be a Calymene. 
I am indebted to the liberality of Dr. J. E. Dekay, of New York, 
for this very curious species. It occurs in a soft grey sandstone, and 
was found in the State of New York, but its precise locality I was 
unable to ascertain. It was probably obtained in Ulster County, 
among the fragments of sandstone, rolled from the Shawangunk 
mountains, and which are so rich in fossil remains. 
Asapnus AstrRaGALOTES.—Green. 
We have met with a perfect fragment of the abdomen and tail 
only, of this striking Asaph. It comprises four distinct costal arch- 
es of the lateral lobes; these are terminated by a narrow well defi- 
ned membranaceous expansion along their outer edges. The ribs 
are broad and faintly grooved on their upper surface; the middle 
lobe is rounded—exceedingly prominent, and terminated rather ab- 
ruptly near the central part of the membranaceous expansion, which 
appears to be supported by a thin short prolongation from it, as in the 
A. micrurus. The upper surface of the whole animal, appears to 
have been covered with minute granulations. 
The fossil from which our description is made, I observed in the 
fine cabinet belonging to the Lyceum of Natural History in the city 
of New York. There is a number of specimens of this species, in 
that important, extensive and liberal institution ; but they are all frag- 
ments, presenting the same general appearance as the one above de- 
scribed. They were obtained from Greenville canal, in Upper Cana- 
da, and are imbedded ina soft dark colored argillaceous shale, asso- 
ciated with other animal remains, some of which are exceedingly 
minute. 
ASAPHUS TETRAGONOCEPHALUS.— Green. 
The buckler of this Asaph, which is still found attached to the 
abdomen, resembles in its contour a long crescent ; the anterior edge 
