150 



THE VOYAGE OF H.M.S. CHALLENGER. 



ance are omitted (even the sex of the specimens not being mentioned), that there is 

 still uncertainty as to the correctness of the identification. 



I therefore add details, which are not given by the original describer, but which 

 will show whether or not the two forms are identical. 



The Slickers (figs. 2, 3) of the sessile arms are nearly hemispherical, with numerous 

 meridional grooves which pass obliquely towards their distal side ; the homy ring is 

 smooth, and the papillary area unusually wide. 



The Suckers of the tentacular club are in about ten rows, hemispherical in form, and 

 mounted on long peduncles (fig. 4) ; the horny ring bears in its distal semicireumference 

 from fifteen to twenty rather irregular conical teeth (fig. 6), and is surrounded by a 

 papillary area with three rows of little spines and two of irregular plates (figs. 5, 7). 



The Shell (figs. 8, 9, 10) is elliptical in outline, except that the posterior extremity 

 is somewhat expanded ; the dorsal surface has fine rugosities disposed in curves parallel 

 to the anterior margin, and a raised ridge passes along its middle ; the chitinous margin 

 appears along the edges, and extends some distance beyond them : it is curved down- 

 wards and inwards laterally, while posteriorly it expands into the hemielliptical plate 

 characteristic of the genus ; the ventral surface is elevated so that the shell is thick, the 

 striated area is not hollowed but has several slight grooves passing along it from back 

 to front ; the last loculus has an index of 33, and is bounded posteriorly by a somewhat 

 irregularly waved line. The inner cone is represented only by a small fillet of calcareous 

 matter from which the limbs pass forwards as thin tapering strips, which extend forwards 

 along only one-third of the striated area. 



The Colour is pale yellowish below, and of a dark slate tint above, with no trace of 

 the remarkable patch over the posterior sac, which is seen in d'Orbigny's figures.^ 



Dimensions. 



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, average, 



Length of first arm. 

 Length of second arm, 

 Length of third arm, 

 Length of fourth arm, 

 Length of tentacle, 



125 mm. 



122 



42 

 28 

 10 



Right. 



Left. 



43 mm. 



42 mm 



35 „ 



36 „ 



40 „ 



40 „ 



45 „ 



35 „ 



70 „ 





■^ Ceph. ao^t.. Seiches, pi. xx. fig. 1, pi. xxii. fig. 1 



