262 
PROCEEDINGS OF THE ACADEMY OF 
ChONETES" MUCRONATA, n. Sp. 
Shell rather large, semicircular, having its greatest breadth on the cardinal 
border, which is usually extended into mucronate angles. Surface ornamented 
by a few sub-imbricating concentric marks of growth, crossed by fine regular 
closely set strise, about one hundred and fifty of which may be counted around 
the border, where eight or nine of them occupy the space of one line. 
Larger valve depressed, having generally a broad, shallow, undefined, mesial 
sinus extending from the front towards the beak. Ears sometimes separated from 
the central region by very shallow depressions, and often slightly curved upwards 
at the extremities. Cardinal margin sloping a little from the beaks, on each 
side of which it is ornamented by from eight to eleven tubular spines, directed 
©bliquely outwards. Area rather wide and, having a broad deltoid aperture, 
with elevated margins. 
Smaller valve following nearly the curve of the other ; beak and central re- 
gion concave ; ears flat ; area rather broad, but narrower than the other, and 
rectilinear. Interior provided with a small very slightly projecting bifid median 
tooth, which nearly closes the aperture of the other valve. From the base of 
this tooth there are five radiating ridges, two of which are rather obscure, and 
extend obliquely outwards near the cardinal edge, while a third extends at right 
angles to the hinge, a little more than half way across towards the front of the 
yalve. The other two ridges are much shorter, and occupy an intermediate po- 
sition between this median ridge and the lateral one, and are directed oblique- 
ly forwards and outwards. The whole interior is more or less granulose, the 
granules near the border being much smaller than the others, and ranged in rows 
parallel to the strias on the outside. Breadth of largest specimen 1.13 in.; length 
0-62 inch. 
This species is very nearly allied to C. Smithn, of Norwood and Pratten, to 
which we we were at first inclined to refer it ; a careful examination, however, 
of a large number of individuals in all conditions of preservation, has satisfied 
us that the striae of the shell now before us are always entirely destitute of the 
pits so characteristic of C. Smithn. Our shell is also much more extended on 
the hinge line, which terminates in more acute angles ; while there are not un- 
frequently eleven, instead of ten tubes on each side of the beak. 
Locality and position, — Near Fort Riley, K. T., Upper Coal Measures. 
AxiNus (ScHizoDus) ovATUs, h. sp. 
Shell ovate, most gibbous slightly in advance of the middle; anterior extrem- 
ity broader than the other, somewhat narrowly rounded; posterior end narrow 
and compressed, obliquely truncate above, sub-angular below. Base semiovate 
in outline, the most prominent part being in advance of the middle; cardinal 
edge very short, straight and horizontal, meeting the obliquely truncate poste- 
rior margin at an angle of about one hundred and thirty degrees. Beaks loca- 
ted slightly in advance of the middle, elevated, and incurved at right angles to 
the hinge, rather distinctly angular down the posterior slopes and obliquely 
towards the lower part of the posterior extremity. Surface unknown. Length 
0-65 inch ; heighth 0-45 inch ; transverse diameter of the two valves 0-20 inch. 
This species appears to be about intermediate between Schizodus truncatus^ 
King, and S. rotundatus, Brown, as represented by figures 27 and 30, plate xv., 
King's Permian fossils of England. From S. rotundatus, it differs in being more 
elongate, less broadly rounded in front, and much more obliquely truncate pos- 
teriorly ; the hinge line is also shorter and more nearly horizontal. It differs 
from ;S'. truncaius in the more nearly central position of the beaks, much shorter 
and less sloping cardinal edge ; while its anterior extremity is more narrowly 
rounded. 
Locality «wc?posz/fiow. —Cottonwood Creek, K. T., high up in Upper Coal Mea- 
sures. 
[Dec. 
