REPORT ON THE PTEROPODA. 
45 
The proboscis of the Pneumonodermatidse being rather elongated, the anterior part 
of the digestive tract is capable of considerable displacement. The cerebro-buccal con- 
nectives are also long in this family (PI. IV. fig. 9, %). 
Family II. Clionopsida 
The family includes only the single genus Clionopsis. 
The Cephalic Region is less elongated in this family than in the preceding. The 
anterior or labial tentacles are short and shaped as in all the Gymnosomata. The pos- 
terior or nuchal tentacles are more conspicuous than in most of these, and are especially 
well developed in Clionopsis hrohni. Like those of the Pneumonodermatidse, they each 
receive two nerves, each terminating in an enlargement. 
The Foot of Clionopsis is characterised by the absence of a posterior lobe ; it presents, 
however, a plicated tubercle, having the same structure as in other Gymnosomata. 
The Visceral Sac exhibits also the glandular dorsal patch, already described in the 
case of the preceding family. 
The Digestive Tract. — As regards these organs, Clionopsis only differs from the 
Pneumonodermatidse in its anterior portion. Indeed the stomach, liver, and intestine 
are disposed identically in the two families, and the anus also opens into a cloacal 
depression near the aperture of the kidney ; this depression is limited anteriorly and to 
the right by the osphradium (PI. IV. fig. 10). 
The anterior part, however, of the digestive tract of Clionopsis is characterised by 
the great elongation of the proboscis and of the oesophagus (the evaginated proboscis of 
Clionopsis has been figured in the systematic portion of this Report). 1 The elongation 
of the oesophagus is a necessary consequence of that of the proboscis, since it has to be 
folded up within the latter when it is everted. 
The proboscis is further characterised by the absence of buccal appendages, which is 
explained by the law of compensation in the organs ; the growth of the proboscis in 
length renders useless the presence of organs of prehension at its base. 
The Respiratory Organs consist, as I have already stated in my systematic Report, 
of a terminal gill in the adult state, a lm ost analogous to that of Pneumonoderma ; the 
lateral gill is absent. 
The Excretory and Circulatory Organs. — Of all the Gymnosomata, Clionopsis is the 
one in which the form of the renal apparatus and its relations with the central circulatory 
organ are the most readily recognisable, owing to the transparency of the integument. 
Its structure and relations have already been accurately described by Gegenbaur. 
The Generative Organs of the Clionopsidae are quite similar to those of the 
Pneumonodermatidae (PI. IV. fig. 8). 
1 Zool. Chall. Exp., part lviii. pi. in. fig. 1. 
