24 THE VOYAGE OF H.M.S. CHALLENGER 



hook (figs. 29, 30). Tlie lateral plates were more slender than in the previous species, the 

 denticles of the posterior edge were quite minute or almost entirely absent (figs. 31, 32, 33, a); 

 the two external plates were almost exactly as in the above-described form (fig. 33, b). 



The oesophagus was wide and enlarged posteriorly into a crop ; there was no second 

 enlargement. The foliated stomach was, as before, very much hollowed anteriorly, 

 and had a dirty brownish-yellow colour. The whole anterior half and lower surface of 

 this stomach was enveloped in the (faintly yellow) white glandular layer; the posterior 

 half of the bulbus pharyngeus, including the radula, was quite covered over by it, as also the 

 whole of the central nervous system. The true stomach was almost completely surrounded 

 by the liver, and was smaller than usual. The intestine exhibited a shorter bend than 

 ordinarily, but was otherwise typical. The contents of the digestive cavity were unrecog- 

 nisable animal remains. 



The liver was very large, of a dirty brown colour, and extended up, under the testis, 

 to the apex of the spiral. The kidney and foliated gland did not differ from those of the 

 previously described species. 



The large yellow testis exhibited the ordinary structure (fig. 34). In the lobules were 

 seen the usual very long, hair-like spermatozoa ; but besides these (figs. 35, 36) others were 

 present, having a length of only 0"1 to 0*2 mm., and in these forms the thicker (attached) 

 end was drawn to a sharp point, the proximal extremity also often terminating in a 

 process. Like the others, they form large, more or less radiating groups. The vas 

 deferens, arising from the testis on the right, not far from the spiral, with several 

 short thick main branches, measured 0"7 to 1 mm. in thickness. It was white in colour, 

 though here and there exhibiting a greenish and iridescent shimmer. It extended 

 forwards for about 12 mm., and then became associated with the very long prostate 

 diverticulum, which was rolled up within the coils of the vas deferens, and which when 

 unrolled measured 4 cm. in length, and - 75 to 1*5 mm. in diameter. The vas deferens 

 extended in a coiled course to the region of the shell-muscle, measuring, when unrolled, 

 about 35 cm., with a diameter of 1 to 075 mm. In these last coils it was more solid and 

 muscular ; then becoming thinner it was continued in small loops, within the body- wall, 

 covered over by a thin muscular layer, to the penis. Here and there, as far as this last 

 stretch, the vas deferens exhibited, like the diverticulum, a greenish shimmer and 

 iridescence. The penis (fig. 38) had the usual long extended form, and a biconvex sec- 

 tion; the end was a little flatter, but hardly at all broader; the opening of the seminal 

 duct lay immediately in front of the rounded point (fig. 38, b) ; the vas deferens, accom- 

 panied by a strongly developed nerve, extended in the usual fashion through the penis. 



This species, probably differing from the preceding in colour, is perhaps also dis- 

 tinguished by the lingual armature, in which the median plates have a more strongly 

 toothed cutting edge and a longer hook, while the lateral plates are, on the whole, more 

 slender, and almost entirely destitute of teeth on the upper edge of the hook. 



