182 



THE VOYAGE OF H.M.S. CHALLENGER. 



Dimensions. 



Length, total, 



End of body to mantle-margin, ventrally. 



End of body to mantle-margin, dorsally, 



End of body to eye, 



Breadth, of body, 



Breadth of head, 



Eye to edge of umbrella, 



Length of fin, . 



Breadth of fin, . 



Diameter of largest sucker on sessile arm. 



Diameter of eye, 



Diameter of lens. 



Length of first arm,^ 

 Length of second arm. 

 Length of third arm. 

 Length of fourth arm, 



96 

 25 

 35 

 40 

 22 

 22 

 12 

 15 

 21 



1 

 15 



7 



Q) 



Eight. 



Left. 



45 mm. 



47 mm 



51 „ 



56 „ 



55 „ 



55 „ 



50 „ 



50 „ 



This form is evidently related both to Histioteuthis and to Calliteuthis, and in many 

 respects is intermediate between them. For instance, while Histioteuthis has a large 

 web, and Calliteuthis none, Histiopsis has a web which reaches about halfway up the 

 arms. The dorsal bands of the siphon are present in Histioteuthis, present in Calli- 

 teuthis, whilst in Histiopsis they are present but concealed, and not obvious except on 

 close examination. 



As regards the presence of a valve in the siphon of these forms there seems to be 

 some uncertainty ; d'Orbigny ^ united the genera Loligopsis, Chiroteuthis, and Histio- 

 teuthis in the famUy Lohgopsidae, which had, amongst other characters, that of being- 

 destitute of a siphonal valve. The first of these genera, as has been already pointed out 

 (p. 46), has no systematic locus standi whatever ; Histioteuthis is usually described 

 as having no valve, as is also CJiiroteuthis by V^rany,' d'Orbigny and Brock,* whilst 

 VerriU in a species described by him from the North Atlantic, which certainly seems 

 to belong to this genus, distinctly affirms that a valve is present. Professor Lankester 

 informs me that in a Chiroteuthis veranyi in University College Museum, London, 

 " there is a very small, in fact, a rudimentary valve, just a transverse fold not projecting 

 much " and also that he has acquired a Histioteuthis with a " well-developed valve in its 

 funnel." From this it seems certain either that an error has been made by some observer 

 or else that one species of Chiroteuthis has a siphonal valve, whilst others have not, 

 which would imply that the systematic value of this structure is very much less than has 

 hitherto been supposed, for its presence or absence has generally been considered as 



' Measured from the centre of the eye. 

 3 Ce-pk medit, p. 120. 



2 C^ph. acet., p. 320. 



* MorphoL Jahrb., Bd. vi. p. 261, 1880. 



