282 DISCOVERY REPORTS 



lines each measuring ca. i mm. in length. Each line contained 10-12 eggs touching one 

 another. At St. 136, also in December, a specimen of L. helicina with an injured gonad 

 showed similar eggs. Spawning specimens were taken in the month of January, in the 

 Terra Nova Expedition (Massy, 1920). Although the largest haul was made at night, 

 heavy catches occurred in the day also. Paulsen, in his plankton investigations in the 

 waters round Iceland, in 1904, has pointed out that the difference between day and night 

 is but slight in the Arctic summer, and he found that Pteropods at Iceland were able to 

 stand daylight and moreover lived on organisms which were dependent on the daylight. 



About one hundred examples from St. 133 from hauls at 50 and 100 m. had pink 

 bodies. Usually the colour is dirty white, the liver and gonad being darker and more 

 variable, while the region about the mouth is very dark. 



Most of the species of this family are very small and have a sinistral shell with a spire 

 more or less developed and a horny operculum, which may be circular or oval. L. heli- 

 cina was described by Phipps nearly 160 years ago under the name of Clio helicina. 

 Arctic specimens are thus described by Sars (1878, p. 399): "Animal atro-purpureum 

 vel obscure violaceum, alls pallidioribus, pellucidis". In the Terra Nova collection of 

 27,000 individuals from the Antarctic, the colour of the body of the animal was found to 

 be lemon-yellow in small specimens, fawn turning brown in larger, and dark brown in 

 all specimens above 2-5 mm. in diameter (Massy, 1920). The shell is very thin and has 

 a low spire of about five or six whorls, with a deep suture. The surface is closely fur- 

 rowed and the shell can reach 8 mm. in size (Meisenheimer, 1905, p. 410). 



Sir C. Eliot (1907, p. 7) found six points of difference between specimens taken by 

 the 'Discovery' in Antarctic waters, which he regarded as L. antarctica, and a large 

 collection of L. helicina from Davis Strait and the North Pacific. 



(i) Antarctic specimens were smaller and the fins were smaller in proportion to the 

 size of the shell. I have found Antarctic specimens, varying in size from 0-5 mm. to 

 6-0 mm. in diameter, and the fins seem to be very variable in size, some being much 

 longer and thinner than others. Probably the state of extension at the time they were 

 killed, and the degree of strength of the different kinds of preserving fluid, would also 

 affect the fins and cause contraction or make them appear long-drawn out and flabby. 



(2) and (3) Striation and umbilical border of shell. Most of the present specimens 

 have lost their shells. In the Terra Nova examples shells with faint spiral striae but 

 with no umbilical border were observed in specimens up to a size of 2-5 mm. Meisen- 

 heimer (1905, p. 410) found that the umbilical border was well marked only in adult 

 specimens and was but feebly developed in specimens of about 3 mm. in diameter. 



(4) Distribution of colour. As already noticed this would seem to vary with age from 

 lemon-yellow to fawn, pink and dark brown. 



(5) Posterior lobe of foot more deeply and distinctly divided. "In the Terra Nova 

 specimens this is certainly the case compared with Boas (1886), fig. 70 of Table 5, but 

 the figures of Vayssiere (1915, pi. vii, figs. 1350 and 136) of the examples of L. helicina 

 from Spitsbergen which he has studied, closely resemble many of the specimens in the 

 present (Terra Nova) collection" (Massy, 1920). 



