PTEROPODA. 
203 
CLATHROCCELIA, n. gen. 
Among the fossils of the Hamilton group from Western New York are 
two specimens of peculiar character, which do not appear to be properly 
referable to any described genus within my knowledge. The general form, as 
the fossil presents but a single face upon the surface of the rock, is that of a 
small, flattened Orthoceras, or a longitudinal section of the same, with rapidly 
expanding walls; but a cursory examination shows that the two sides are not 
equally diverging from the apex, one being in a nearly vertical line and 
the other more oblique. The shell has apparently not been cylindrical, but 
may have been of a flattened, triangular or semi-conical form. The interior 
is marked by regular arching bands, which, as seen through the translucent 
shell, have the appearance of septa. These septa are unequally arched, the 
longer limb of the arch extending to the more sloping side of the shell, while 
the shorter limb extends to the straighter side of the shell, and, before reaching 
the margin, is recurved, and turns slightly backward or towards the apex. 
The straighter margin is likewise a little recurved towards the exposed face of 
the fossil. The latter feature, however, may be due to compression. 
The slight recurving of the septa resembles, in a considerable degree, the 
arching of the chambers in the septate sheath of Bhragmnthec.a Boliemica of 
Barrande ; but our specimens are rigidly straight, and possess other features 
not conforming to that genus. Besides the arching, transverse lines or septa 
there are several, at least four or five, longitudinal lines or laminae, which cross 
the others, and apparently penetrate the interior in like manner. These 
longitudinal lines give to the space included between the two central ones in 
the upper part of the shell the appearance of a siphuncle, but they are in 
nowise different from those on either side; and this apparent condition is 
modified as the lines become less conspicuous towards the aperture of the 
shell. 
In the obliquely arching outline of the aperture, this fossil is somewhat 
similar to some forms of Hyolithes ; but the character of the shell and the 
