52 
THE VOYAGE OF H.M.S. CHALLENGER. 
my systematic Report on the Gymnosomata, I have stated 1 how in Halopsyche the 
absence of a cephalic hood, shaped like that of Clione, is due to the great development 
of the buccal appendages ; and how, in consequence of this, the buccal opening of 
Halopsyche corresponds with the false lips of the latter genus and the anterior tentacles 
are situated upon a common base with the buccal appendages. As regards the posterior 
tentacles, I may refer to the same work. 
I have also, in that part of my Report, described the form of the foot, which exhibits 
the same parts as the corresponding organ in other Gymnosomata. Its two antero- 
lateral symmetrical lobes, situated ventrally to the mouth, were regarded by Souleyet , 2 
Owen , 3 and others as tentacles. But since they are innervated by the pedal ganglia, 
they clearly belong to the foot, as Huxley 4 was the first to point out. 
The envelop of the body presents a thickening which has neither the same structure 
nor the same morphological value as that which is known as the “cartilaginous shell” 
in the Cymbuliidae, since it is situated in the visceral sac and not in the mantle, which 
is entirely wanting in Halopsyche as in all the Gymnosomata. From this point of view, 
therefore, as from any other, there is nothing to justify an approximation of Halopsychidae 
to the Cymbuliidse. 
The Digestive Tract. — The absence of the proboscis is explained by the great 
development of the buccal appendages in the same way as the contrary fact is explained 
in Clionopsis. The mouth opening leads then directly into the buccal mass, which is 
constructed on the same plan as in other Gymnosomata, except as regards the hook-sacs, 
whose absence is due to the lack of the proboscis. 
The salivary glands, somewhat elongated, appear in transverse sections of the head. 
The stomach resembles in form that of all the Gymnosomata, and has no masticatory 
organs whatever, a fact which shows clearly that Halopsyche has no relation with the 
Thecosomata. The intestine is a little longer than in the preceding genera, but ends on 
the right side 5 in the same position as in them. 
The Respiratory and Circulatory Organs. — Souleyet regarded the buccal appendages 
as two gills, but as a matter of fact, branchiae are entirely wanting in Halopsyche as in 
Clione. I suppose that respiration must be brought as in Clione according to Wagner, 
for the structure of the body wall, as seen in transverse sections, is the same as he 
represents in the case of Clione. 6 
The heart, according to Souleyet , 7 is situated in the middle line, at the base of the 
cephalic appendages, which he regarded as gills. Nothing of the kind is the case. On 
1 Zool. Chall. Exp., part lxv. p. 53. 2 Voyage de la Bonite, Zoologie, t. ii. p. 243, pi. xv. fig. 3, l. 
3 Mollusca, Encyclopaedia Britannica, 8th ed., vol. xv. p. 361, fig. 40, d. 
* On the Morphology of the Cephalous Mollusca, Phil. Trans., 1853, p. 41, pi. iv. fig. 3, ms. 
6 Not on the left side, as said by Huxley, loc. cit., p. 41. 
0 Die Wirbellosen des weissen Meeres, Bd. i. pi. x. fig. 3. 
7 Voyage de la Bonite, Zoologie, t. ii. p. 247. 
