312 Cincinnatt Society of Natural History. 
ward. The facet for the reception of the second radial forms a semi- 
circular depression in the middle of the upper part, and occupies 
about one half of the summit and extends down more than one third 
the length of the plates. Sutures, except between the basals, are im- 
pressed or distinctly channeled, and the surface is covered with well- 
defined nodes. ‘I'wo rows on the pentagonal base surround the colum- 
nar facet, and two rows occur on the first radials below the semicircu- 
lar facet for the second radial. 
This species is founded upon a single specimen, showing only the 
parts above described. It has some weight, in connection with the 
other species of crinoids, as evidence, in determining the age of the 
rocks, and can, no doubt, be readily identified, imperfect as the type 
specimen may be. 
TREMATOPORA AMERICANA, D. Sp. 
' Plate VII., fig. 5, fragment natural size; fig. 5a, magnified view. 
This species consists of irregularly cylindrical, ramose, hollow 
stems or branches. The interior is evidently lined with an epitheca. 
The diameter ofthe stems examined is from two tenths to six tenths of 
an inch, and the thickness of the corallum is from less than half a line 
toaline. The thickening of the corallum is not dependent upon the 
size of the branches, but seems to be the result of irregular growth. 
The cell tubes are subcircular and irregularly distributed. The aper- 
tures are margined by a projecting lip which sometimes overshadows 
the lower part of the opening. There are usually about four cell tubes 
in one tenth of an inch where the intervening spaces are about one 
and a half times the diameter of the tubes, but owing to the scattered 
distribution of the tubes, the proportion is variable. There is neither 
uniformity in the shape of the branches, nor in the order of a _ahge- 
ment of the cells. 
TREMATODISCUS ROCKYMONTANUS, 0. Sp. 
Plate VII., fig. 6, view, natural size. 
Sheil medium size, discoidal; umbilicus wide, showing the inner 
whorls and perforated in the middle; volutions very gradually increas- 
ing in size, narrower transversely than from the dorsal to the ventral 
side, and slightly embracing; septa slightly arching forward on the 
periphery, and surface ornamented by fine revolving lines. Siphuncle 
and body chamber unknown. It is supposed that about one whorl has 
been broken from the specimen described and illustrated. 
