t72 PROCEEDINGS OF THE NATIONAL MUSEUM. tol. 38. 



Gill cavity and branchial complex. — The large thin-roofed branchial 

 cavity opens by a long and narrow crescentic horizontal slit just 

 above the nuchal fold. On opening it the most conspicuous objecl 

 is the osphradium running diagonally across the left side of the roof 

 and consisting of a double scries of leaflets (PL 21, fig. 10) set on 

 either side of a central rhachis after the usual fashion, hut very large 

 and having the side edges and basal edges of the leaflets black. It 

 differs markedly in the shape of the leaflets (which are distinctly 

 bilobed) from the other species of the genus. Beside it, on the right, 

 the gill, though larger, is much less conspicuous, lis thin leaflets, 

 colored like the neighboring tissue, arranged in a single row on the 

 right of the rhachis, are long and narrow compared with those of 

 the other species of the genus, and simply pointed. The anus was 

 not satisfactorily made out, the right-hand part of the roof of the 

 gill cavity (where it doubtless lies, as in the other species) having 

 been disturbed in the examination of other parts. 



Genital system. This was only examined externally, but nothing 

 appeals to casl doubt on its substantial conformity with the other 

 species of the genus. The female genital opening was not satis- 

 factorily made out, the region near the anus where it, should occur 

 having been disturbed, as above stated. The penis (PI. 22, fig. 1) is 

 extremely large (quite double, in proportion, that figured or described 

 for the other species) and ot herwise peculiar. Arising from the nuchal 

 fold on the right side of the neck, above and just to the left of the 

 base of the right tentacle, is a massive base as thick as the base of the 

 tentacle itself and half again as long as broad, directed backward 

 and slightly outward and upward. Sharply turning more than a 

 right angle (so that it runs forward, and slightly outward and down- 

 ward) the organ now rapidly diminishes in size to a slender neck of 

 less than a quarter the original diameter. The minimum size is, 

 however, scarcely reached before the organ suddenly swells again 

 (though this time only slightly) at the same time acquiring along its 

 external margin a great crest recalling in form and proportion, the 

 conventional mane of the chess knight. The crest rapidly diminishes 

 and at the point where it is lost tin' organ suddenly bends directly 

 back upon itself, at the same time diminishing to a point which 

 reaches back to the level where the crest began. A fair idea of the 

 relations of tin' parts can be given by comparing the whole structure 

 to an arm, the upper arm enormously fat, the forearm stinting fat 

 but rapidly dwindling to a thin w rist . the hand and fingers very long, 

 and the back of the hand expanded into a high crest. In attitude 

 the arm must be strongly Hexed and the lingers pressed together at 

 the tips and impossibly Hexed so as nearly to touch the inside of the 



wrist. The finer structure was not examined. Bergh has minutely 

 described it for the related specie-. 



Head. The broadly ovoid body mass i- bounded in front by a 

 strong nuchal fold clearly marking the transition to the head region, 



