A. M 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 irapei-fectly 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 ' 

 also appear to be essentially the same as in the genus last named. 



Ommastrephes. 



Ommastrephes (2}ars)W0rbignj, 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 have 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. 



