ON THREE INTERESTING NEW OEGOPSIDS FROM THE BAY OF SAGAMI. 143 
The present species resembles in many respects all the species of Om- 
mastcrpJics hitherto known { 0. sagittatiis, O. hazciieiisis, O. sloain), to which 
it seems to stand in the nearest relationship among the Oegopsida, especially 
is this so with regard to the fact that the hectocotylus is only in the right 
ventral arm, and the siphonal groove has the foveola in front, bounded pos- 
teriorly by a cresentic pocket-like fold without any folds outside. Characters 
distinguishable from these species are shown in the following key, which was 
made by means of a comparison of the specimens whose mantle-lengths are 
about 148-215 mm. 
1. Foveola of siphonal groove with several longitudinal folds within. 
Breadth of mantle about i8-3o"/o of its length. Fins together distinctly 
broader than their length. Horny rings of arm-suckers provided with several 
sharp teeth on their distal margins, without any quadrangular supplemental 
teeth alternating with the preceding ones. Horny ring of largest tentacular 
sucker generally with quadrangular supplemental teeth alternating with sharp, 
ordinary teeth. Hectocotylus showed only by the degeneration of suckers 
and the swelling of the sucker bases 
O. sagittatus, 0. hazvaiensis, O. sloani. 
2. Foveola of siphonal groove without longitudinal folds within, but 
smooth. Breadth of mantle lö-ig'Vn of its length. Fins distinctly longer 
than their total breadth, attenuated posteriorly. Piorny rings of arm-suckers 
varying in denticulation in different suckers of each arm ; largest sucker of 
II arm jorovided with quadrangular supplemental teeth alternating with long, 
sharp, ordinary teeth. Horny ring of largest tentacular sucker with only 
sharp, and without any supplemental, teeth. Hectocotylus shown not only 
by the degeneration of suckers and the swelling of sucker bases, but also 
by the thickening and enlarging of ventral protective membrane and by 
sculpture composed of pits and transverse grooves on outer surface 
Oinmastreplics volatiUs n. sp. 
