134 THE VOYAGE OF H.M.S. CHALLENGEE. 



left is somewhat broader than the right. The ^mantle-margin extends far over the head 

 dorsally and is not emarginate, but slightly undulating ventrally. The siphon is short, 

 terminating far short of the depression between the ventral arms. 

 TJie Head is broad, and the eyes very prominent. 



The Arms are subequal, the order of length being 4, 1, 2, 3 ; they are one-fourth 

 the length of the body, all are flattened and taper evenly to fine points. The suckers 

 are in four series (fig. 4), except in the right dorsal arm, where they appear to be in 

 two, probably owing to its state of extreme compression ; they are of medium size, many 

 are deeply notched proximally and distally, and provided with fine meridional grooves 

 on the margin (fig. 6) ; the horny ring is smooth and surrounded by a papillary area. 

 The hectocotylus was not seen, the only specimen being a female. The umbrella is 

 small, widest between the lateral arms, where it reaches up to the sixth or seventh row 

 of suckers. The buccal membrane has five distinct points, the ventral edge being 

 thickened and forming a large folded spermatic pad (fig. 3) ; it bears no suckers. The 

 outer lip is thick, and marked with fine longitudinal grooves ; the inner is papUlate. 



The Tentacles are as long as the mantle, with a three-sided flattened stem, much 

 broader proximally than distally. The club is slightly expanded, with a narrow 

 protective membrane belo^w, a broad one above, and a distinct web outwardly (fig. .5). 

 There are five or six series of suckers, slightly larger in the middle than at the margins, 

 on very long slender peduncles; the horny ring is smooth. 



The Surface bears a number of small irregularly scattered papdlse, and four or five 

 elongated warts on the dorsum near the origin of the fins, and some folds in the skin 

 on the ventral surface ; probably these are due to contraction. 



The Colour is a dull grey with a bluish shade above inclining to yellow 

 below. 



The Jaivs are shown in figs. 7, 8. 



Tlie Shell (figs. 9—11) has an elongate oval outline, broadest one-third of the way 

 back and rounded ofi" at both ends. The free chitinous margin is narrow anteriorly, 

 then broader, evanescent posteriorly, a deep calcareous outer cone forming the posterior 

 extremity of the shell; it is but slightly exposed on the dorsal surface, which bears only 

 faint indications of a median ridge, and is beset with fine granules disposed in rows parallel 

 to the anterior margin. The ventral surface is elevated so as to give the shell a more 

 than average thickness; the last loculus has an index of 33, and is bounded by a tran verse 

 hemielliptical curve; the striated area is excavated, but slightly convex in the middle 

 line. The inner cone consists only of the slightly elevated limbs, which run along 

 three-quarters of the striated area and unite with each other as a fiattened fillet 

 posteriorly. The spine has lost its extreme point, but it is strong, and has a raised 

 knife-like ridge developed upon its ventral aspect^ (fig. 11). 



' Whence the specific name. 



