22 3 
A. E. Terrill — North American Cephalopods. 
large denticles ; inner lateral teeth with two unequal points ; two 
outer laterals simple, slender. Eyes as in Ommast replies. 
This group is related on one side to Arehiteuthis , on the other to 
Ommast replies. The armature of the tentacular-arms will distinguish 
it from the latter, and the large caudal tin and broad membrane of the 
sessile arms from the former.* The dentition of the type is peculiar, 
so far as known. In addition to the typical species, this genus 
will doubtless include several species with marginal webs, that have 
hitherto been referred to Ommast replies ; but they are mostly too in- 
definitely described and figured to show the special characters referred 
to. Thus, 0. pteropus Steenstrup belongs to this genus, if a specimen 
from Bermuda, now in my possession, be correctly identified.! 
Sthenoteuthis megaptera Yen-ill. 
Arehiteuthis megaptera Yen-ill. Amer. Journ. Science, vol. xvi, p. 207. 1S78. Tryon, 
Manual of Conchology. vol. i. p. 187 (description copied from preceding papen. 
Plate XXI, figures 1-9. 
Much smaller than the species of Arehiteuthis , the total length 
ot' the body and head being but nineteen inches. Body relatively 
short and thick. Caudal fin more than twice as broad as long, the 
length about half that of the body. Its form is nearly rhombic, with 
the lateral angles produced and rounded, and the posterior angle 
very obtuse, the posterior edge, as preserved, being slightly concave. 
The ventral anterior edge of the mantle is concave ceutrally, with 
a slight angle to either side, about 7 5 inch from the center; from 
these angles it is again concave to the sides; on the dorsal side the 
edge advances farther forward than beneath, terminating in a slightly 
prominent, obtuse angle in the middle of the dorsal edge. The ex- 
ternal ear consists of a slightly elevated, transverse lamina, with three 
thicker and much more elevated lamina? which extend forward, on 
the head, one in the median liue of the eye, with one above and one 
below it, the lower one longest and least elevated, curving downward 
beneath the head. The two upper ones are broadly rounded at top. 
Behind the transverse fold there is a deep, irregularly crescent-shaped 
fossa. The eye-sockets are large, oblong, and furnished with distinct 
* According to the statement of Gerrais, Arehiteuthis dux has similar membranes. 
f &. Rirtramii ( Ommastrephes Iiartramii (Leach) D’Orb. ) also belongs to this genus, 
but is a more slender species. It has the characteristic smooth suckers and tubercles 
on the wrist of the ‘club,’ and a very broad caudal fin. It lives in the region of the 
Gulf Stream. 
