L'JI "TERRA NOVA" EXPEDITION. 



persistent characters in tin 1 present specimens. The thickness of the integuments is 

 also verv evident, while there is a distinct neck behind the tins instead of between or 

 above them as in < '. limacina. In the large haul at Station 323, when the tow-net was 

 down for a month, there were about a dozen specimens which were quite different in 

 appearance to the rest. They were narrower aud very transparent, and with a crimson 

 instead of an orange coloured gonad, and were without larval rings, although not large. 

 Their radula and hooks were just like those of the others, however, and a careful search 

 amongst these revealed a few forms partly intermediate between the two types. 

 Probably the transparent form was the result of overcrowding and want of sufficient 

 nourishment owing to the net having been down for a mouth, so that the earliest caught 

 specimens were likely to have been hemmed in and pressed down by later arrivals. 

 Distribution. Antarctic seas. 



FAMILY PNEUMODERMATIDAE. 



GENUS PNEUMODERMA, Cuvier, 1804. 



2. Pneumoderma atlanticum, Bounevie. Fie. 7. 



o 



Pneumoderma atlantica, Bonnevie, 1913. 



Station 62, N. Atlantic, near Equator, one. 



This measures 4 mm. and is nearly colour- 

 less, with white opaque spots. The posterior 

 lobe of the foot possesses a tubercle. The 

 radula is 4-0-4 and the suckers number at least 

 fifty on each appendage. The latter are some- 

 what triangular and the largest suckers (which 

 are about four times the size of the smallest) 

 are placed towards the middle. The specimen 

 is much contracted, and in the effort of dissecting 

 out the buccnl parts I failed to find out how 

 the appendages are attached to the proboscis. 

 Bounevie (191:5, p. 09) states that P. atlanticum 

 "is distinguished from other species of the genus, 

 inter alia, by the acetabuliferous appendages 

 being fixed to the proboscis." This statement 



vy 



atlanticum (Bonn.). 



A. 

 r IG. i . PneuvnodeTinci ....,.... ,, y^^ui-i.y. 



A, entire animal, ventral aspect, x 16 ; is Dot vel T clear = as the appendages in question 

 /.;/., lateral gill ; p.y., posterior gill, are usually fixed to the proboscis in all the 



B, posterior gill, enlarged. Pterota (Pelseueer, 1887, p. 6, fig. 1. Pnni- 

 monoderma) ; and on p. 81 n/>. <_//., under Pmumonodernut, we read " Buccal appendages. 

 Two symmetrical appendages latero-ventrally inserted ou the proboscis.' From Mile. 

 Bonuevie's illustrations (op. cit., pi. VI, tigs. 49 and 50) of /'. atlnnticnin, the appendages 



