525 
II. Thecosomata inoperculata ( Carinaridce ). Animal in great 
part naked, but having the visceral mass- protected by a shell. 
1. Shell corneous, with an involute nucleus. Swimming-plate 
nearly opposite the visceral mass. Metapodium with filiform 
appendage — Cardiapoda. 
2. Shell calcareous with spiral nucleus. Swimming-plate con- 
siderably in advance of the visceral mass. Metapodium 
laterally compressed without filiform appendage — Cari- 
naria. 
III. Thecosomata operculata ( Atlantidce .) 
1. Shell corneous with an involute nucleus. Operculum subtrigonal, 
with small lateral subapical nucleus — Oxygyrus. 
2. Shell calcareous with a spiral nucleus. Operculum oval, with 
a large median subapical nucleus — Atlanta. 
After describing the several characters of the order as regards 
external configuration, eyes, and auditory sacs, the author called 
attention to the rachidian teeth as being capable of furnishing good 
generic characters, for which they are especially valuable, as they 
often outlive the decay of the soft parts. 
To avoid undue extension of his paper, the author selected for 
special description the genera Firoloides and Atlanta, which occupy, 
according to his views, the two extremes of the group; and he de- 
scribed in detail, and illustrated by coloured drawings, the anatomy 
of a species of Firoloides which he had met with in Bass’s Strait, 
and the anatomy of Atlanta, with reference to all the species of 
the genus, adding to these some observations on the other genera, 
and deferring questions of specific determination to a future paper. 
4. On the Structure of Chondracanthus Lophii ; with Obser- 
vations on its Larval Form. By William Turner, M.B., 
and H. S. Wilson, M.D., Demonstrators of Anatomy. 
The authors, after a brief historical introduction, proceeded to give 
a detailed account of the anatomy of this parasitic crustacean, the 
description comprising that of the female and male, and, so far as 
they had been enabled to trace it, of the larva also. 
FeMALE. — Average length, ^ inch ; breadth, ^th inch — divided 
into cephalic, thoracic, and abdominal portions. Cephalic part 
presented on each side a lateral process ; at the anterior margin a 
