REPORT ON THE MARSENIATLE. 17 



margin was almost median ; the upper surface of the mantle almost even ; the border as 

 usual, or somewhat narrower, with the ordinary radiating stripes on the lower surface. 

 The shell 1 had a normal relative size, a small and but slightly protruding spiral, with the 

 last turn extremely large. The shell was not specially thin, but somewhat hyaline, of a 

 white colour, and exhibiting fine lines of growth. The internal (shell) surface of the 

 mantle was quite colourless. 



On removing the shell the muscle-facettes were seen as usual (fig. 2), and the superior 

 visceral mass was arranged in the ordinary fashion. The pale yellowish-white reproduc- 

 tive organ (testis) (fig. 2, b), somewhat whiter at the extremity, lay posteriorly. At the 

 posterior edge of the visceral mass, the stomach (fig. 2, a) and intestine were seen shining 

 through. In front of the testis was placed the greyish foliated gland, through which the 

 intestine with its wdiite excrement masses (fig. 2, c) could be seen, while in front of the 

 former extended a broad white stripe of secreted substance. Further forward lay the 

 bow-shaped branchia, at its left end the small kidney (fig. 2, d) and the pericardium, with 

 the heart shining through. In front of the gill the unusually large olfactory organ 

 was situated (fig. 2, e). Through the roof of the inferior visceral mass or floor of the 

 respiratory cavity, the viscera could be seen very much as usual ; in front, the bulbus 

 pharyngeus filling about half of the space, with the radula-sheath rolled up behind it, 

 and further back the yellow " foliated stomach." 



The central nervous system was of unusual relative size. The ganglia were in other 

 respects exactly as in the typical Marsenice, except that the infra-intestinal was perhaps 

 somewhat larger ; the pedal somewhat shorter and more triangular, possessing besides 

 the usual secondary, short-stalked ganglion on the anterior end. The tentacles and eyes 

 were as in the other Marsenice (fig. 1). The otocysts also appeared as usual, with round, 

 milk-white sheaths, lying just outside the pedal ganglia. They measured approximately 

 0'08 mm., and enclosed a yellowish otolith of about - 05 mm. in diameter. The 

 olfactory organ was, as we have mentioned, unusually large, exhibiting on each side 

 about 20 rather thick folia. 



The bulbus pharyngeus had the usual form, and was of a whitish colour ; the cartila- 

 ginous patches were distinct, and the yellowish mandibular plates were perhaps a little 

 longer than in the typical species. The tongue had the usual character, and possessed 

 11 rows of tooth plates, of which the 5 foremost were more or less injured. The radula- 

 sheath was fully twice as long as the bulbus, and contained 28 developed, and 5 younger 

 rows of teeth, making altogether 44. The plates were very faintly yellow ; the median 

 had a maximum length of 0-088 mm., with a breadth of 0'06 mm. ; and the lateral were 

 - 12 mm. long. The median plates (figs. 4, 5, a) were longer than in the typical species ; 

 the hook and denticles (2-4 on each side) were typical, the left limb also a little longer than 



1 Owing to the minute size of the animal, it was impossible to remove the shell without breaking the last 

 whorl. 



(ZOOL. CHALL. ESP. PAET XLI. — 1886.) Ss 3 



