CEPHALOPODA OF THE CRETACEOUS MARLS. 247 
sidered the inner face of the volution as the dorsal, which is perhaps 
correct enough in speaking of the animal, but Dr. Tuomey says the septa 
shows on the back a recurved lip, which, if we consider the back the outer 
surface or edge of the volution, as is usually done, this is entirely wrong 
for this cast, as the septa extend directly across the back and over to the 
septal process in an almost straight line. Therefore, if Dr. Tuomey’s de- 
scription is correct for his species, which I have never seen, this one must 
be an entirely distinct species. I shall at any rate consider it as A. pau- 
cifex of Cope, and disregard Dr. Tuomey’s name until further evidence is 
obtained. If they prove identical Dr. Tuomey’s name has precedence, as 
it was given in 1854, while Dr. Cope’s name dates only from 1866. The 
present shell may be more fully described as follows: 
Shell large, somewhat ponderous, ventricose, with a broadly rounded 
back and convex sides; umbilicus slightly impressed, but not open, the 
inner edge of the lip rather overlapping the one within, and the outer volu- 
tion embracing the imner to that extent; aperture large, forming half of a 
long ellipse, being rounded on the outer margin and gradually expanding 
to the edge of the umbilical depression or for nearly four-fifths of the entire 
length of the opening. On the inner side it is strongly modified by the 
projection of the inner volution; entire length of the apertural opening 54 
inches on the specimen; greatest width across nearly 4 inches. Septa 
strong, deeply concave and distant, being nearly 3 inches apart on the back 
of the specimen described at the third chamber, and nine chambers only 
visible to the volution; lateral septal processes situated nearer to the outer 
margin than to the umbilicus, and are large, strong, slightly directed out- 
ward from a circular line half as wide across the origin as long, that of the 
second septum shown on the specimen being 2 inches long from the curve 
of the inner portion of the septum and 1} inches on the outer side. Inner 
portion of the septal line moderately arched forward between the umbilical 
line and the septal process (or lateral lobe) and reaching slightly in advance 
of the outer division, which from the base of the process or lobe extends 
almost directly across the back of the shell; siphon rather large, measuring 
more than a quarter of an inch in diameter at the outer chamber, cylindrical 
as far as can be seen; situated at about one-fifth or a little more than one- 
