CEPHALOPODS OF WESTERN NORTH AMERICA. 



295 



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Fig. s- — Loltgo opal^iLCns, camera 

 drawing of oral aspect of tentac- 

 ular sucker of 9 ', from a mount itl 

 balsam. [loi.] 



3=2, 4, I. Umbrella rudimentary between all the arms except the ventral pair, where it is totally lack- 

 ing; continued upon the dorsal margins of the dorsal arms as a prominent membranous keel; inner 

 margins of second arms bluntly carinate, third arms obsctu-ely so; outer margins of second and third 

 arms with a fleshy keel nmning to their tips; ventral arms provided ^ 



with a very broad and prominent web along the outer margin, ensheath- 

 ing the base of the tentacle, and thence gradually narrowing toward 

 the tip; a similar but much less developed keel extends along the inner 

 margins of the ventral arms. Along the sucker-bearing surface of all 

 the arms runs a delicate membranous swimming web, strengthened 

 by numerous slender transverse trabeculae of a muscular natiu-e, occm-- 

 ring in alternation with the sucker pedicels. Save on the ventral pair, 

 where it becomes much reduced, this web is exceedingly prominent 

 on all the arms, but attains its maximum development on the third 

 pair, where its diameter is seen in well-preserved specimens to be 

 as great or greater than that of the arm itself (pi. 

 XLVi, fig. 4, 5). Suckers small, somewhat kettle- 

 shaped, regularly alternating in two rows, obliquely 

 poised on rather short conical pedicels; margin of 

 cupules hood-like, with a small sinus in the supe- 

 rior margin; honiy rings with nine to twelve bluntly rounded, squarish teeth on the 

 upper margin; papillary area wide and very prominent in microscopical prepara- 

 tions (pi. xuii, fig. 8). 



Left ventral arm in the male conspicuously hectocotylized; along tlie proximal 

 two-thirds of the arm the suckers (about twenty pairs) are unmodified, but along 

 the distal third their pedicels become transversely flattened and elongate, the cups 

 showing a simultaneous diminution in size, a condition especially true of the 

 suckers at the extreme distal end of the outer row, where the cups are reduced to 

 mere rudiments. Tow;ird the end of the inner row the pedicels decrease in size 

 and resume their normal shape, the cups decreasing comparatively little, so that 

 the suckers at the extreme distal end of the row are more nearly normal. The 

 outer row is still further unique, in that some six to eight of the more proximal 

 suckers undergoing modification are much more elevated and have broader pedicels 

 than either tlaose opposite or those succeeding or following them; indeed, throughout 

 the modification of each pedicel and sucker in this row is more complete than that 

 of the corresponding sucker of the inner row (pi. XLin, fig. 7). 



Tentacles of moderate but variable length, highly contractile; the club but 

 slightly expanded, lanceolate, furnished with a pronounced keel and a narrow swim- 

 ming membrane (text fig. 4). Suckers in four rows, those of the two outermost 

 very small; those of the two median rows much larger, their homy rings armed 

 all round with about thirty-five small, rather elongate, bluntly conical teeth (text 



Buccal membrane seven pointed, each point bearing two distinct rows of very 

 minute crowded suckers, seven to nine in a row. The latter have well-developed 

 papillary areas and homy rings with five or six irregularly squarish teeth. There 

 is also an inner buccal membrane like a thickened, radially rugose cushion sur- 

 rounding the beak (pi. XLin, fig. 6). 



Gladius thin, broadly lanceolate; midrib slender; slight lateral but no marginal 

 thickenings (text fig. 6). 



Color in life not observed; color in alcohol a pale buff, with numerous very distinct and beautiful 

 brownish chromatophores scattered profusely over the whole dorsal surface, and in somewhat less degree 

 over the ventral as well. 



?1G. 6. — Loligo 

 opalescens, dor- 

 sal aspect of 

 gladius. [69.] 



