124 THE VOYAGE OF H.M.S. CHALLENGER. 



and posteriorly these two fillets unite and often form a little pointed space into whicli 

 the hinder end of the visceral sac is received ; this I have called the " inner cone," 

 because in many cases the margin of the shell proper forms a larger more or less com- 

 plete cone outside this, which is called the "outer cone." (See PL XXI. figs. 14, 15.) 

 The two fillets above described will be alluded to as the " limbs of the inner cone." 



The suckers, also, in this genus ofi"er valuable characters for the discrimination of 

 species ; they are always pedunculate and obliquely set, as in most Decapoda, but the 

 horny ring surrounding the acetabular cavity may be either smooth or more or 

 less coarsely toothed. Steenstrup has pointed out that this denticulation is in some 

 cases subject to a sexual variation, so that in instituting comparisons between dijfferent 

 forms in respect of this character, care must be taken not to use difi"erent seses. The 

 ring is commonly surrounded by an area in which the epidermal cells are surmounted 

 by rough plates of a chitinous material ; this I propose to call the " papillary area." 

 The relative sizes and shapes of its component parts vary in different species, and in many 

 cases I have figured them. Furthermore, the margin of the sucker itself is in many 

 species marked by a number of narrow grooves, separating more bulging intermediate 

 portions; these, from their direction, will be called "meridional grooves," and will 

 be alluded to in those cases in which their presence has been observed. 



The structure of the hectocotylised arm has been described and figured, wherever it 

 was present ; and so far from this being uniform throughout the genus, no less than 

 four different types of modification have been observed. It is very unfortunate that we 

 have accurate information on this point in so few forms of this genus, for there is no 

 doubt that it would afford a most valuable character in the discrimination of species. 



I regret that I have been unable in the present work to adopt the divisions of the 

 genus proposed by Dr. deEochebrune in his recent " Etude monographique;"-"- from some 

 of his conclusions I am obliged to differ entirely, as for example the separation of 

 Diphtherosepion ornatum (Eang), from the genus Sepiella, and having been unable to go 

 fuUy into the whole question it appeared to me better to leave the genus intact, except 

 in so far as specimens, which I have myself examined, seemed to require a difli'erent 

 treatment. 



Sepia smithi,^ Hoyle (PL XVI. figs. 1-12). 



1885. Sepia Smithi, Hoyle, Diagnoses I., p. 190. 

 1885. „ „ Hoyle, Prelim. Rep. L, p. 294. 



Habitat. — Station 188, Arafura Sea, south of Papua, September 10, 1874 ; lat. 

 9° 59' S., long. 139° 42' E.; 28 fathoms; green mud. Four specimens, $. 



1 Bull. Soe. Philom. Paris, s^r. 7, t. viii. pp. 74-122, pis. iii.-vi. 



2 Named after Mr. Edgar A. Smith, F.Z.S. , of the British Museum, whose investigation of the collections made 

 by H.M.S. "Alert," has made us acquainted with several new and interesting Cephalopods. 



