138 



THE VOYAGE OF H.M.S. CHALLENGEK. 



the ventral aspect ; the tip of the arm bears two series of small suckers. The umhrella 

 is better developed than usual, its greatest extent (between the lateral arms) being up 

 to the eighth rows of suckers. The buccal membrane has the usual seven points, but not 

 very strongly marked ; the outer lip is smooth and thin, the i?iner papUlate. 



The Tentacle is as long as the head and body together, with a slender and some- 

 what flattened stem ; the club (fig. 3) is short and rather broad, and has a protective 

 membrane on either side of the suckers, and a broad web on the dorsal asj)ect, extend- 

 ing for a distance equal to half its length down the stem ; there are from six to eight 

 rows of very minute suckers, subequal, and with smooth horny rings. 



The Surface is smooth, except that on one side of the ventral surface are three 

 slightly raised linear ridges, apparently due to contraction, and a few minute papillae 

 on the dorsal surface posteriorly. 



The Colour is on the whole pale, yellowish below, purplish above. 



The Jaios are shown in figs. 9, 10. 



TJie Shell (figs. 11-13) is hemielliptical in outline anteriorly, tapering to a point 

 behind. The chitinous margin is rather broad, widest about two-thirds back ; it is 

 bare over all except the median third of the dorsal surface, which is finely rugose, 

 and has a slightly elevated median portion and a faint linear ridge in the middle line 

 posteriorly, about 3 mm. long, and terminating 2 mm. from the base of the spine. The 

 ventral surface is but little elevated ; the last loculus occupies more than one-third of 

 it, and its posterior boundary is almost semicircular, inflected in the centre. The 

 inner cone is evanescent ; its limbs are chitinous and form ■ a ventral margin to the 

 terminal cone. A spine is present, but, as it had been broken ofi", its length and form 

 cannot be determined. 



Dimensions. 



Length, total, . ' 



End of body to mantle-margin. 



End of body to eye, 



Breadth of body, 



Breadth of head. 



Eye to edge of umbrella, 



Breadth of fin, . 



Diameter of largest sucker on sessile arm. 



Diameter of largest sucker on tentacle, 



Length of shell, . 



Breadth of shell, 



Length of first arm, 

 Length of second arm, . 

 Length of third arm, 

 Length of fourth arm, . 

 Length of tentacle, 



112 mm, 

 45 

 49 

 25 

 22 

 12 



5 



0-5 



0-16 

 52 

 21 



Eight. 



Left. 



22 mm. 



22 mm 



23 „ 



23 „ 



24 „ 



24 „ 



26 „ 



25 „ 



65 „ 



63 „ 



