MUSEUM OF COMPARATIVE ZOOLOGY. IV. 



OPISTHOTEUTHIS Vekrill, gen. nov. 



Body broad, depressed, closely united to the brachial web except at the 

 posterior end, which projects slightly. Fins long, attached at about the middle 

 of the body, near the dorsal surface ; bases wide apart, each supported by a 

 distinct transverse cartilage. Siphon small, projecting slightly from beneath 

 the posterior end of the body, and directed backward, with a very small aper- 

 ture. Head as broad as the body ; eyes large. The lower surfoce of the head 

 and body wholly attached to the brachial membranes. Arms subeciual, united 

 together to near their tips by a very broad, thick, soft web, which leaves only 

 the inner surface of the arms exposed ; suckers in a single row, those toward 

 the base of the arms largest. On each side and alternating with the suckers is 

 a row of small, tapered cirri ; these commence in a rudimentary form between 

 the first two suckers, and continue from there to the tips. 



Opisthoteuthis Agassizii Verrill, sp. nov. 



Plate I. Fig. 1. Plate II. Fig. 1. 



The body is broad, depressed, rounded posteriorly, and with the head is 

 wholly adnate to the web connecting the arms, except at the posterior end 

 behind the fins, where it is slightly free and overhangs a little ; the siphon 

 projects backward beneath the posterior end in the groove thus formed ; the 

 Ijranchial opening appears to have been small, partially surrounding the siphon, 

 but the membranes in this region are much mutilated, so that its form and 

 extent cannot be determined. The fins are large, thin, wide apart, elongated, 

 oblong ovate in form, the outer end bluntly rounded, each fin is supported by 

 a separate internal cartilage, of which tJie inner end is broadest and thick, while 

 the outer end extending into the free portion of the fin is much thinner, lanceo- 

 late, tapering to a blunt point ; this cartilage is situated much nearer to the 

 posterior than to the anterior edge of the fin and does not extend much beyond 

 its middle, leaving the terminal third thin and flexible. The head is about as 

 large and as broad as the body ; the eyes are very large and occupy the entire 

 sides of the head. As seen from above the arms are concealed except at the 

 tip by a thick, soft web, which unites them together and unites them closely to 

 the sides of the head and body. The integument of the entire upper surface is 

 very soft and flabby, and appeai-s to have been smooth, although it is much 

 wrinkled in the alcoholic specimen ; the web between the arms extends to 

 near the end, leaving only about one fifth free, and this portion is bordered by 

 a membranous fold along each side. The web consists of an outer and inner 

 portion, separated by considerable thickness ; the inner membrane arises from 

 the inner surface of the arms, which projects but little above it. The arms are 

 rather large and moderately stout along the middle portion, much narrowed 

 toward the bases, which are. not in contact ; the free ends are rather slender, 



VOL. XI. —NO. 5. 8 



