A. E. Verrill — North American Cephalopods. 
267 
Ommastrephes. The eye-balls were large and somewhat oblong in 
form, and appear to have been nearly two inches broad and three 
long. The eye-lids are badly mutilated, but the anterior sinus can 
be imperfectly made out. It seems to have been broad and rounded. 
The aquiferous cavities appear to have been like those of Omma- 
strephes. The form and structure of the cartilaginous ‘ brain-box 5 
also appear to be essentially the same as in the genus last named. 
Ommastrephes. 
Ommastrephes (pars) D’Orbigny, Voy. Am. Merid., 1835; Cephal. Acetabulifers, p. 341. 
Body elongated, pointed posteriorly. Caudal fin broad, trans- 
versely rhomboidal. Pen narrowed behind the middle, with a strong 
median rib and large marginal ribs on each side ; near the posterior 
end thin and concave, expanded into a lanceolate form, with the tip 
infolded and slightly hooded. Head large. Eyes with lids, having 
a distinct sinus in front. 
Arms stout, the third pair stoutest, with a dorsal keel ; all the 
arms haA’e marginal membranes 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 contractile, 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 denticu- 
late suckers only ; distal part of club with four to eight rows of small 
denticulate suckers. 
Siphon-tube placed in a depression of 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. 
Mantle-fastenings (‘apparatus of resistance’), situated on the basal 
extension of the siphon, consist, on the ventral side, of two large 
triangular bosses, with an elongated and somewhat ear-shaped longi- 
tudinal fosse, and a shallower transverse one ; and on each side of the 
inner surface of the mantle, of a corresponding short, raised, longi- 
tudinal ridge, swollen posteriorly, and a lower transverse ridge, 
which fit closely into the fosses. The dorsal side of the head 
has a median, longitudinal facet, that fits upon its counterpart 
on the mantle, over the anterior part of the pen, which gives it 
support. 
Trans. Conn. Acad., Vol. V. 
33 
June, 1880. 
