PTEROPODA. 



13 



These specimens found by the ' Discovery ' seem referable to Cl. (iiitarctica, E. A. 

 Smith (/. c.). They can hardly be identified with Cl. longicaudata, Cl. flavewnx or 

 Cl. punctata, because those species, though imperfectly known, are said to have only one 

 or two, and not three pairs of buccal cones. In my opinion they are also specifically 

 distinguishable from Clioue Umncimi, though the species are, no doubt, nearly allied. 

 The superficial difference in appearance is striking, and the divergent characters of the 

 two species may be tabulated as follows : 



CLIONE ANTARCTICA. 



1. The part of the body behind the fins is shorter 



than in the Arctic form. A specimen 18 mm. 

 long consists of G mm. head and fins + 

 12 rnm. body. 

 There is a distinct neck behind the fins. 



2. Considerably smaller than the Arctic form. Few 



individuals exceed 20 mm., even when arti- 

 ficially extended. E. A. Smith gives 22 mm. 

 as the length ; presumably the maximum of 

 his specimens. 



3. The integuments are thicker, firmer, and less 



transparent than in the Arctic form. In 

 most specimens they are plentifully be- 

 sprinkled with opaque yellow spots, some- 

 times a little raised. 



4. Three, or at least two, larval rings are habitually 



present in individuals measuring 15 mm. or 

 more in length. 



5. The base of attachment for the anterior lobes 



of the foot is a narrow band. The posterior 

 lobe is larger and stouter in proportion to the 

 anterior lobes than it is in Clione limacina. 



G. There is an interval between the dorsal cone 

 and the other two. The median cone is the 

 largest. 



7. Median tooth very small, and present only in 



hindmost rows of radula. Laterals in hind- 

 most rows have forked bases. The number 

 of laterals gradually increases from 3 to 8, 

 the innermost teeth of the half row being 

 sometimes rudimentary. 



8. Penis small, and presence of accessory organ 



doubtful, though not disproved. 



0. The visceral mass extends backwards almost 

 into the posterior third of the body. 



CLIONE LIMACINA. 



1. A specimen 18 mm. long consists of 2'5 mm. 



head and fins + 15 -5 body. 

 The broadest part of the body is just behind 

 the fins, and as far as there is a neck it is 

 between or above the fins. 



2. Specimens -40-45 mm. in length are frequent. 



3. The integuments are thin and transparent. 



Though spots are present they are not con- 

 spicuous, and as a rule can only be seen when 

 carefully sought for. The whole animal is 

 flabby, and almost gelatinous. 



4. No larval rings found in individuals measuring 



as much as 10 mm. When traces of the 

 posterior ring are found in small specimens it 

 is not shaped as in Clione antarctica. 



5. The base of attachment for the anterior lobes is 



broad. 



G. The cones are equidistant. The dorsal is the 

 largest and the ventral smallest. 



7. Median tooth larger, and present in all or most 

 rows. Laterals with forked bases not found. 

 The number of laterals does not increase so 

 markedly, and the rudimentary teeth are 

 found at the outer ends of the rows. 



8. Penis proportionately much larger, and provided 

 with a large accessory organ. 



!). The visceral ma?s is more compact .and rounded, 

 extending only a little way behind the fins. 



