212 1. E. Terrill — Xorth American Cephalopoda. 
a roughened or slightly corrugated and decidedly excavated area 
between it and the cutting edges; the cutting edge below this ridge 
is nearly straight, or slightly convex; the notch at its base is 
rounded and deep and strongly excavated at bottom : the tooth is 
broad, stout, obtusely rounded at 'Ummit. sloping abruptlv on the 
side of the notch, and gradually to the alar edge. The anterior edge 
of the ahe. beyond the tooth, is rounded and stronglv striated ob- 
liquely: it makes, with the cutting edge, an angle of about 110°. 
The innner surfaces of the two sides of the internal plate of the 
rostrum form an angle of about 45°. 
The lower jaw of Xo. 1 Plate XVIII. fig. 3) is represented cmlv 
by it' anterior part, the ahe and gular lamime having been cut a wav 
by the person who removed it.* It agrees very well in form and color 
with the corresponding parts of the one ju>: scri > some- 
what 'mailer. The lateral ridges of the rostrum are rather more 
prominent, and the area within it is narrower and more deeply exca- 
vated. especially at the base of the notch, where the excavation goes 
considerably lower than the inner margin. The notch is narrower 
and not so much rounded at its bottom. The tooth is about the same 
in size as that of Xo. 10, and appears to be even more prominent, 
because the anterior edge of the alae is more concave at its outer 
base ; it is also more compressed and less regularly rounded at sum- 
mit. This jaw measures 32*5™“ (130 inches) from the tip to the pos- 
terior ventral border of mentum ; 17 from the tip to the bottom 
of the notch; 4^™ from bottom of notch to tip of the tooth. 
Both these lower jaws agree in having a very prominent tooth on 
the alar edge, with a large and deeply excavated notch between it 
and the cutting edge of the beak, and in this respect differ from the 
lower jaw of A. Harvey i , for in the latter the tooth or lobe is broad 
and less prominent, while the notch is narrower and shallower. 
This -cents to be the best character for distinguishing the jaws of 
the two species. But they also differ in the angle between the alar 
edge and the cutting edge of the rostrum, especially of the lower 
jaw. for while in A. Harvey i this is hardly more than a ric:ht angle, 
in A. princep* it is about 110°. Moreover, the darker color and 
firmer texture of the jaws of the latter seem to be characteristic. 
To this species I have referred the Catalina specimen (Xo. 14, 
p. Is9), preserved in the Xew York Aquarium. The jaws of the latter, 
which were examined and carefully measured by me, agree very 
* The specimen ~as given to the Smithsonian Institution bv Mr. G. P. "Whitman, 
of Boc-kpon. Mass- in 1S72. )Xo. 2524). 
