REPOET ON THE PTEROPODA. 
29 
As to the argument based on the relative height of the spire, the average proportion 
40 32 
of height to maximum diameter is 27 i n Limacina balea, and 27 in Heterofusus 
retroversus. But in Spinalis goulclii, Stimpson, identified by Sars with Limacina balea , 
and with very well marked transverse striation, the apparently very exact figure given 
31 
by Stimpson 1 exhibits the above ratio as yy less, that is to say, than that of Hetero- 
fusus retroversus, while in Scsea stenogyra, with smooth surface, the ratio according 
37 
to Philippi's figure is 
It is thus seen that the relative height of the spire varies as well as the striation of 
the surface, and that the variations of these two features are independent. We are, 
therefore, led to conclude that Limacina balea and Heterofusus retroversus are not two 
specifically distinct forms, but belong to a single species which exhibits a certain number 
of varieties. 
# 9 . Limacina trochiformis (d’Orbigny). 
1836. Atlanta troclnformis , d’Orbigny, Voyage dans lAmerique meridionale, t. v. p. 177, 
pi. xii. figs. 29-31. 
1840. Sjnrialis trochiformis, Eydoux et Souleyet, Description sommaire de quelques Pteropodes 
nouveaux ou imparfaitement connus, Revue Zoologique, t. iii. 
p. 237. 
1850. Limacina trochiformis, Gray, Catalogue of the Mollusca in the Collection of the British 
Museum, pt. ii., Pteropoda, p. 33. 
1852. Limacina naticoides, Rang, Histoire naturelle des Mollusques Pteropodes, pi. x. figs. 1, 2. 
For description and figures see Souleyet . 2 
The umbilicus of the shell is very small in this species. The dorsal (anterior) margin 
of the fin does not exhibit any tentacle-like lobe. 
Habitat . — Atlantic Ocean, from 41° N. to 28° S.; Mediterranean, Naples (where 
I have often observed it alive), Malta (David Bruce); the shell has been dredged at a 
great number of localities in the Mediterranean — Crete (Jeffreys), &c.; Indian Ocean, 
south-east of Arabia (Blanford); Pacific Ocean, China Sea (Gray), Malay Archipelago 
(Copenhagen Museum); Equatorial Pacific to 152° W.; South-east Pacific to 30° S. 
(d’Orbigny). 
Challenger Specimens. — I. Living specimens. 
Between Stations 162 and 163, April 3, 1874; Melbourne to Sydney; lat. 38° 7 ' S., 
long. 149° 18' E. 
Station 216 a, February 16, 1875 ; north of New Guinea; lat. 2 ° 56 ' N., 
long. 134° 11 ' E. 
1 Shells of New England, pi. i. fig. 4. 
2 Voyage de la Bonite, Zoologie, t. ii. p. 223, pi. xiii. figs. 27-34. 
