IO XUDIBRANCHIATE GASTEROPODA. 



and not broad; neither the upper nor the lower surface themselves seemed to send off nerves, but 

 from the fore margin and the outer end, on the contrary, at least 7 nerves arose, from the indentation 

 on the outer margin three, and from the hindmost part of the lower side of the commissure arose a 

 quite thin nerve running backward. The pleural ganglia were almost but half the size of the 

 cerebral ones, of a short-oval contour (fig. 2 bb.i; they sent off four thicker and a pair of quite thin 

 nerves. The pyrifonn pedal ganglia (fig. 2 cc) that were connected, as it were, by a stalk with the 

 cerebral ones, were larger than the pleural; they sent off four strong nerves, one from the lower side. 

 The large common commissure (ca. 25" 1 " 1 long), as usual double (fig. 2 d). The eerebro-buceal connective is 

 almost as long as the large commissure; the buccal ganglia (fig. 2ee) were of an ovally roundish shape 

 with a diameter of 2'5'" m , and sent off five nerves; the rather strong buccal commissure (fig. 2 fj was 

 20 mm long. — The nerve cells (of the pleural ganglia) were of a diameter of at least o-30 mm ; the nerves 

 were in their proximal part often a little reddish. In the skin was seen a rather rich network of 

 nerves and small ganglia, sending off branches to the small papillae of the skin '). 



In spite of a careful examination I did no more in this individual than in the earlier examined 

 one svicceed in finding eyes and otocysts, which nevertheless surely are not wanting 2 ). The strongly 

 developed rhinophores showed along the fore and hinder surface a strong median (transversely folded) 

 rhachis, downwards broad and upwards tapering, from which arise lamellse without spicules; the point 

 of the club is formed by a little final papilla. Through a special cavity two strong nerves ascended, 

 and besides strong and anastomosing muscular strings stretched through these organs. The small, 

 round disks of the skin were slightly depressed, with a projecting edge, and in the middle was often 

 found a more or less contracted papula (pi. I, fig. 3). No spicules or calcified elements were found in 

 the skin at all. 



The mouth-tube of this individual was quite short, the bulbus pharyngeus being projected, 

 so that the bluish labial disk was lying in the outer mouth; the labial disk was short-oval, longer 

 in the direction from above downwards, its diameter was i2 m "\ in the middle was seen the narrow, 

 perpendicular aperture of the inner mouth (pi. I, fig- 2). The exceedingly powerful bit lb us pharyn- 

 geus itself (pi. I, fig- 4; pi- II, fig- ib) was of a whitish colour; only in the region of the pharynx the 

 underlying colour shone through with a bluish tint; the bulb was 34"" long by a breadth of 3-2 cm and 

 a height of 3 cm ; the radula sheath projecting in a semiglobular form posteriorly on the lower surface 

 (fig. 4c) had at its base a diameter of i3 mm . The rather strong Aim. bulbo-tubales (Protrusores 

 bulbi) were as has been shown before 3). The bulbus pharyngeus (fig. 4) is by a rather sharp crest 

 (the margin of the mandibles), only interrupted on the lower surface, divided into a smaller and nar- 

 rower former part, and a rather larger hinder part; on the sides behind the mentioned crest the latter 

 has an even hollow, posteriorly passing evenly into the common prominences produced by the tongue- 

 muscles to the sides of the pharynx. The upper side of the bulbus pharyngeus (fig. 1) is strongly 



>) Comp. I.e. p. 112. pi. XIV, tig. 5. 



j es are found in a species of Pleurotoma . obtained at a depth of 2090 faths, in a Fusits from a depth of 1207 

 faths iWyy. Thomson, the Depths of the v Sea. 1873. p. 465) and in other mollusks; the presence of eyes in animals from these 

 depths will, according to 'the abyssal theory of light , not be incomprehensible. On the other hand a rather large number 

 of blind deep-sea fishes and a still greater number of abyssal Crustacea without eves have been found. (Comp. Semper, 

 Die nat. Existenzbed. d. Thiere, I. 1880. pp. 103, 262). 



3) Comp. I.e. ]). 113, pi. XIII, fig. 2. 



