DESCRIPTION OF OPISTHOTEU'l'Hl« DEPRHSSA X. SP. 333 



whose edge is capa1)Je of being clasped l)y the above mentioned button 

 of the corresponding side. 



It is convenient for description's vsake to speak of two branchial 

 chambers, each containinii' a cnll and which communicate with each 



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other, provided the Ijuttons are fixed, by only a narrow space at the 

 inner end of the siphon. From this connecting space the two 

 branchial chambers extend divero'entlv forwards and laterallv for a 

 distance of about 11 mm. They overlie tlie connective tissue of the 

 umbrella, clasp from behind tlie visceral mass and are superiorly 

 covered by the mantle (iiuui., tig. 7) which strictly speaking represents 

 their ventral wall. On the floor of the connecting space and right at 

 the inner end of the siphon, there is a medianly situated, rounded 

 elevation, Ijearing the anus, discernible as a blackish spot («//., tig. 7). 

 The said elevation is posteriorly closely embraced by a thin fold, 

 likewise of the floor, and is superiorly directly continuous with tlie 

 median septum {x(p.) that divides the entrances into the two branchial 

 chambers. 



Each of the latter is widest near the siphon-base and narrows 

 antero-laterally to a cleft-like terminal portion. The widest portion 

 is occupied by an extremely shortened gill ((ji.), which is attached to 

 the membranous anterior wall enclosing the visceral mass (r./r.). 

 Thus the sill is directel backwards or ventrad. Around its short 

 rachis are grouped together the lobular lamelke, so that the entire 

 organ is reniform and presents an appearance not unlike that of half 

 of a peeled orange. There are in all six lamellœ to each gill, but the 

 one most medianly situated is very rudimentary and can not be 

 observed when seen from above. 



It was of course very desirable to determine the sex of our 

 specimen. Although there was no sign of hectocotylization on any 

 of the arms, we discovered immediately on opening the mantle-cavity, 



