REPORT ON THE PTEROPODA. 
13 
Gray (1850), 1 Gould (1852), 2 and Boas (1886) 3 have tried to simplify the matter by 
uniting all the known species in a single genus with the oldest title, Limacina, Cuvier. 
But it must be noted that Gould knew but few species of Limacinidse, and that for one 
form which he regarded as new he even thought that it might be well to create a new 
genus. Jeffreys 4 also unites in a single genus, Limacina, all the species which he discusses 
except Atlanta inflata, d’Orbigny, for which he establishes a genus Embolus, although a 
certain species which he calls Limacina. i differs more from the typical Limacina than does 
Atlanta inflata. And besides, as we shall afterwards see, that solution of the difficulty 
which seeks to unite in a single genus all the living Limacinidse is not in conformity 
with the differences of organisation exhibited by the various types. 
There is only one way of restoring order to the confused nomenclature, and that is to 
find for each generic title the connotation given to it by its inventor, and the type to 
which it was originally applied. In this way alone can one recognise with any certainty 
what are the synonymous titles, and eliminate the more recent tautologies. 
Let us then see what titles ought to be expelled from the nomenclature. 
I. It is necessary first of all to abstract the genus Agadina, Gould, which, as we shall 
immediately see, has been too inadequately and imperfectly diagnosed to admit of any 
accurate conception being framed in regard to the organisms to which it ought to be 
applied. 
II. The genus Spiratella was founded in 1824 by de Blainville for Clio helicina, 
Phipps. But for the same species the genus Limacina was erected by Cuvier in 1817. 
The name Spiratella need not therefore be retained. 
III. The genera llcliconoides, d’Orbigny (1836), Spirialis, Eydoux and Souleyet 
(1840), and Helicophora, Gray (1842), are all based upon the same series of small forms, 
but without reference to any particular type. This series includes among its species 
three forms of shell, and to this it is due that the above titles have been used with 
different connotations by different authors (the brothers Adams, Bronn, Carus, Fol, 
Sars, &c.). 
These forms of shell are — (1) a more or less elevated spiral with a simple lip ; (2) a 
depressed spiral with a rostrated lip ; and (3) with a very large aperture and a columella 
prolonged into the rostrum ; and they have all received different names. The adoption 
of these new names evidently involves the abandonment of the titles noted above in the 
original sense of their authors. The new names corresponding to the three forms of shell 
are as follows : — 
1 Catalogue of the Mollusca in the Collection of the British Museum, pt. ii., Pteropoda. 
2 The Mollusca and Shells of the U.S. Exploring Expedition. 
3 Spolia atlantica. 
4 New an d peculiar Mollusca, &c., procured in the “ Valorous ” Expedition, Ann. and Mag. Nat. Hist., ser. 4, 
vol. xix. p. 337. 
