26 
THE VOYAGE OF H.M.S. CHALLENGEK. 
with the last whorl much expanded and convex, and projecting more in proportion than 
all the foregoing. Aperture quadrangular, somewhat angled in front ; columella straight, 
reflected to the right ; umbilicus broad. 
Colour. — Milky. 
Dimensions. — 2 to 2 # 5 mm. in height, about 1*5 mm. in maximum diameter. 
Operculum approximately oval, with an almost straight columellar margin, and with a 
spiral portion measuring barely two-fifths of the entire length. 
The animal exhibits a small lobe on the dorsal margin of each fin. 
Habitat. — Cape Horn (Souleyet). 
From its discovery by Souleyet this species was not reobserved until the Challenger 
Expedition. Jeffreys 1 follows Y^rany in noting the coast of Piedmont as a locality of 
Spirialis australis, and this has been repeated without question by various authors . 2 
The statement is, however, entirely erroneous, and has in all probability reference to 
Limacina trochiformis. 
The specimens collected by the Challenger show that this species has a somewhat 
wide distribution round the South Pole, where it occupies, along with Limacina 
antarctica, a position analogous to that of Limacina retroversa and Limacina helicina in 
the north. 
Challenger Specimens. — Living. 
Station 146, December 29, 1873; Marion Island to Crozets; lat. 46° 46' S., long. 
45° 31' E. 
Station 149, January 9, 1874 ; at Kerguelen Island; lat. 49° 8' S., long. 70° 12' E. 
Station 150, February 2, 1874 ; Heard Island; lat. 52° 4' S., long. 71° 22' E. 
Between Stations 154 and 155, February 21, 1874; in vicinity of Antarctic Ice; 
lat. 63° 30' S., long. 89° 8' E. 
Observations. — Boas 3 has expressed hesitation in regard to the possible specific 
identity of Limacina australis, Limacina retroversa, and Limacina trochiformis. They 
are, however, as we shall see, three very distinct forms. 
In the first place, as regards Limacina trochiformis, it belongs along with Limacina 
bulimoides to a special group of Limacinse quite different from that to which Limacina 
australis and Limacina retroversa are to be referred. It is characterised by the presence 
of a shell with oval, rounded aperture, with the columellar margin reflected to the left, 
and with a very narrow umbilicus. In Limacina bulimoides and Limacina trochiformis 
also the animal is without any lobe on the fin. In Limacina australis, on the other hand, 
the opening of the shell is quadrangular, with the columellar margin reflected to the 
right, with a very broad umbilicus, and a tentacle-like lobe on the dorsal margin of the 
1 On the Marine Testacea of the Piedmontese Coast, Ann. and Mag. Nat. Hist., ser. 2, vol. xvii. p. 180. 
2 For instance Weinkauff, Die Conchylien des Mittelmeeres, t. ii. p. 428. 
3 Spolia atlantica, p. 46. 
