256 PALEONTOLOGY OF NEW JERSEY. 
two, on the largest specimen in hand; but they vary in size and complica- 
tion according to their position; that dividing the first sinus being about 
equal in form and size to the seventh lateral lobe. The first sinus is large 
and broad, each of its main divisions about equal in size to the third sinus: 
Mr. Meek says in his Invert. Pal, p. 467, middle paragraph: 
On comparing authentic specimens from New Jersey with others of nearly 
equal sizes from the Upper Missouri Cretaceous, they are found to agree well in 
form as well as in all essential specific characters of the septa. The New Jersey 
specimens generally have the septa less crowded and the lobes and sinuses propor- 
tionally somewhat shorter; but it is evident that no specific, or even subspecific, 
distinction can be based on such trivial differences. 
The large specimen now before me, which belongs to the collection of 
the Acad. Nat. Sci., Phila., was probably also in Mr. Meek’s hands while 
writing, and was in all probability compared with the diagram of the septum 
given of a western specimen, on page 466 of his work. But if any reliance 
whatever is to be placed upon the details of the septa of ammonites of simi- 
lar character for specific relations or differences, I can not see why these 
two should be considered as being specifically identical. There is not the 
slightest resemblance in detail between them, only a general resemblance. 
In fact, almost the direct opposite of details prevails between the two when 
examined side by side. The lobes in the New Jersey specimen all have 
very narrow, constricted necks with a broad expansion below, while his 
diagram shows a wide neck, usually narrowed gradually toward the ends, 
the lateral branches decreasing in size from above downward in all the 
principal lobes. The sinuses, which are broad, compact, and clavate in the 
New Jersey form, are narrower and much less conspicuous in his figure, 
with the divisions slender, lax, and contorted. If the two specimens are 
specifically alike, what reliance can be placed upon detail of septa for the 
identification of species? None of the New Jersey examples which I have 
seen show any indications of the lines of nodes on the side of the shell as 
in the western forms. To be sure they are all casts, but even on the casts 
of the western forms these nodes are usually indicated, and on comparison 
I find the differences in septa quite general as between them, and I am in- 
clined to conclude that they are either distinct species, or that those features 
which he with many others have considered as grounds for generic divi- 
