[81] CEPIIALOPODS OF NORTHEASTERN COAST OF AMERICA. 
ribs; anterior and posterior portions expanded, the latter with the edges 
involute, and forming a terminal hood or hollow cone. 
OMMASTREPHES D’Orbigny (restricted). 
Ommastreplies {pars) D’Orbigny, Voy. Am. Mdrid., 1835; Cdplial. Ac6tab., p. 341. 
Tllex and Todarodes Steenstrup, Oversigt K. Danske Vidensk. Selsk. Forbandl., 1880, 
p. 90. 
Body elongated, pointed posteriorly. Caudal fin broad, transversely 
rhomboidal. Pen narrowed behind the middle, with a strong median 
riband large marginal ribs on each side; near the posterior end thin and 
concave, expanded into a lanceolate form; at the tip involute and slightly 
hooded. Head large. Eyes with lids, having a distinct sinus in front. 
Arms stout, the third pair usually stoutest, with a dorsal keel; all the 
arms have marginal membranes, strengthened by transverse muscular 
ridges, exterior to the suckers. Suckers of the arms deep and oblique, 
with horny rims, which are strongly denticulate on the outer margin, 
the median tooth usually largest. Tentacular arms rather long and con¬ 
tractile, stout, with a moderately wide terminal club, which has along its 
middle region two rows of large central suckers, and a row of smaller 
marginal ones alternating with them on each side; proximal part of 
club with small denticulated suckers only; distal part of club with four 
to eight rows of small denticulated suckers. 
Siphon-tube placed in a groove on the under side of the head, and 
attached to the head by a lateral bridle on each side behind the eyes, 
and by a pair of bridles .on its dorsal surface, at the bottom of the 
depression in which it is lodged. Terminal orifice transversely elliptical, 
furnished with an internal valve. The depression back of the siphon 
is smooth in our species, in some other species longitudinally furrowed. 
Mantle-fastenings (“apparatus of resistance”), situated ou the basal 
extension of the siphon, consist of two large triangular bosses, each 
with an elongated and somewhat ear-shaped longitudinal fosse, and a 
shallower transverse one. On each side of the inner surface of the 
mantle is a corresponding T-shaped cartilage, consisting of a short, 
raised, longitudinal ridge, swollen posteriorly, and a lower transverse 
ridge, which fit closely into the fosses on the siphon. The dorsal side 
of the head has a median longitudinal facet, that fits upon its coun¬ 
terpart on the mantle, over the anterior part of the pen, which gives it 
support. 
The nuchal crests are formed by a transverse tegumentary fold 
behind the eyes, from which run backward, on each side, three longi¬ 
tudinal lamellae, which are delicate, and have a sensory (perhaps olfac¬ 
tory) function. 
Buccal membrane seven-angled, thin, corrugated ou the inner surface, 
destitute of suckers. 
Branchial auricles and gills large. Liver massive, stomach and coecal 
appendage voluminous. 
