12 
THE VOYAGE OF H.M.S. CHALLENGER. 
| = Atlanta lesueurii, d’Orbigny. 
\ = Atlanta injlata, d’Orbigny. 
J 
= Atlanta reticulata, d’Orbigny. 
To these known species I can also add a new form included in the Challenger 
collection, which may without hesitation be referred to Group II. of undoubted 
Limacinidse. Another form, which cannot be identified with any of those hitherto 
known, seemed at first to be referable to Group III. above, but subsequent examination 
has shown that it must rather be placed in Group I. aloug with another species of the 
same nature. 
How are these different species to be distributed throughout the family ? Or, in 
other words, how many distinct genera can be distinguished. 
The question is indeed a most difficult one, and there are almost as many opinions on 
the subject as there are investigators of the group. Very few of the expressed opinions, 
however, claim much serious attention, for there has hardly been any previous attempt to 
make a systematic synthesis of the family Limacinidse. 
If we turn to the table of genera (p. 8) we see that twelve generic titles have been 
invented for living Thecosomata with spiral twisting, that is to say, just the same 
number of genera as there are certainly admissible species. I append the titles in 
chronological order : — 
Atlanta rangii, d’Orbigny (?), . 
Spirialis ventricosa, Eydoux and Souleyet, 
Spirialis rostralis, Eydoux and Souleyet, 
Protomedea elata, 0 . G. Costa, 
Limacina scaphoidea, Gould, . 
P eracle physoides, Forbes, 
Spirialis clathrata, Eydoux and Souleyet, 
Spirialis recurvirostra, A. Costa, 
1. Limacina, Cuvier, 1817. 
2. Heterofusus, Fleming, 1823. 
3. Spiratella, de Blainville, 1824, 
4. Heliconoides, d’Orbigny, 1836. 
5. Spirialis, Eydoux and Souleyet, 1840. 
6. Helicophora, Gray, 1842. 
7. P eracle, Forbes, 1844. 
8. Scsea, Philippi, 1844. 
9. Campylonaus, Gray, 1847. 
10. Euromus, A. and H. Adams, 1858. 
11. Protomedea, 0. G. Costa, 1861. 
12. Embolus, Jeffreys, 1869. 
What increases the confusion resulting from this superfluity of generic nomenclature 
in a group with so few forms, is the fact that several of these names have been used 
in different ways by different authors. Hence a complex and contradictory set of 
synonyms. 
