Boone, MoUusca,.Cruises of "Eagle" and "Ara," 1921-28 169 



The eye is large, highly developed, the pupils large, although the 

 opening between the lids is usually rather small. The aperture is 

 usually slit-like, the anterior sinus is narrowed and extended down- 

 ward and forward. Both eyelids are well developed. The living eye 

 is a deep blue-black like a jewel. 



The mantle is thick, very muscular, with its anterior margin con- 

 cave beneath, forming almost an angle on each side, above which it 

 advances to the median dorsal lobe, which is very slight. The caudal 

 fin is transversely rhomboidal, wider than long, tapered to an angle 

 posteriorly ; usually its breadth is less than half the length of the body. 



The sessile arms are all four pairs short, their length decreasing in 

 the order 2, 3, 4, 1, counting from the dorsal pair, which are the 

 shortest; the second to third pairs are nearly equal; the fourth pair 

 is normally intermediate between the first and second pairs. All have 

 the suckers similar, and all are provided along their inner angles out- 

 side the suckers, with similar marginal membranes, which are of about 

 the same height as the suckers. Just proximal to each sucker on the 

 inner face of the arm arises a thickened, transverse, muscular fold 

 that reaches to the edge of the lateral membrane; the margin of the 

 latter between these folds is frequently concave, having a scalloped 

 appearance. The suckers are in two alternating rows, becoming 

 smaller and more crowded on the distal two-fifths ; the teeth of a large 

 sucker are figured. 



In living specimens the tentacular arms are quite long; when ex- 

 tended they reach back to the caudal fin. Proximally the arm is 

 rounded trapezoidal, tapered distally. Along the upper outer edge a 

 thin fold runs from the base to tip, forming a wider carina on the back 

 of the club ; two less-distinct folds run along the inner angles, defining 

 a narrow inner face throughout its entire length. This face bears no 

 suekers except near where it begins to expand into the club ; along the 

 margins of the club the membrane widens, reaching a level with the 

 suekers. In the middle region of the club there are two rows of large 

 suckers and alternating with these on each margin is a row of very 

 small ones. The upper of the two rows of large suckers usually has 

 one to two more suckers, and the suckers are larger than those of the 

 lower row. In the present specimen there are seven in the upper, six 

 in the lower line. The suckers in midway each series are the largest 

 and have the edge of the marginal ring more nearly smooth; at each 

 end of each row the suckers decrease in size, and in these the marginal 

 ring becomes denticulate, with rather broad, blunt denticles on the 



