138 MOLLUSCA. 
fiesh-coloured, more or less speckled with purplish ; the 
under parts of the arms were bluish-grey ; the suckers whit- 
ish.” The specimens which furnished an opportunity for 
making the preceding observations, were met with in the 
Gulph of Guinea, and afterwards on the voyage, swimming © 
in a small argonauta, on the surface of the sea. The reader, 
who is desirous of farther information on this subject, may 
consult Dr. Leach’s Observations on the Genus Ocythoe of 
Rafinesque, Sir E. Home on the Distinguishing Characters 
between the Ova of the Sepia, and those of the Vermes Tes- 
tacea that live in water, in the Philosophical Transactions 
for 1817, art. xxii. and xxiii., (both of which are added to 
the appendix of Captain Tuckey’s Narrative,) and a paper 
by Mr. Say, on the genus Ocythoe, in the Phil. Trans. 
1819, art. vii. More recently, however, naturalists seem 
disposed to reunite the Ocythoe with the Argonauta, though 
the question cannot be considered as determined. 
Crass I].—PTEROPODA. 
Fins formed of membranaceous expansions. 
This class was instituted by Cuvier, for the reception of 
a few genera, the peculiar characters of which indicated the 
impropriety of suffering them to remain in any of those 
categories which had been previously established. All 
the species are small in size; and the attempts hitherto 
made to investigate their internal structure, have, in a great 
measure, failed in explaining the functions of the organs 
which are exhibited. The valuable papers of Cuvier, on 
the Clio, Pneumodermon and Hyalea, include nearly all the 
accurate information on the subject, of which naturalists 
are in possession. 
