478 
PALEONTOLOGY OF NEW YORE. 
elongate lateral saddle, the apex of which is almost precisely in the centre. 
of the lateral face of the volution, and much in advance of the summit of the 
umbilical saddle; on the outside of this is another lobe similar to the first, 
and a peripheral saddle in which the summit is still more advanced than- the 
one on the umbilieal margin, and less advanced than the central one. These 
characters of the lateral face are better shown in figure 12 of plate 72 than in 
the figures on plate 73. The suture-lines are strongly marked and usually 
deeply impressed upon the weathered surfaces. Siphuncle minute; not 
satisfactorily determined. 
Test and surface-markings unknown. Upon the peripheral margins of 
some of the casts there is an impression indicative of the imprint of curving 
strise, which may mark the margins of the sinus. 
The internal casts are smooth, wi-th the exception of the deep indentation 
along the suture lines. The fossil usually occurs in a fragmentary condition, 
and few entire individuals have been observed. These measure from sixty 
to sixty-five mm. in their greatest diameter; but fragments of other indi¬ 
viduals of larger size indicate that the shell has had a diameter of eighty or 
ninety mm., exclusive of the chamber of habitation. The slender and much 
expanded form has rendered it more easily broken and dismembered than the 
other species with which it is associated. 
This species is quite unlike any other known to me in our formations, 
though presenting, in its septa, some general resemblance to G. Chemungensis. 
Formation and locality. This species occurs in the same association with G. 
Ixion , in the Goniatite limestone, at Rockford, Indiana. 
