Prof. G. J. Allman on the Anatomy of Actzeon. 161 
In accordance therefore with this arrangement, the Nudi- 
branchiate Mollusca will stand as follows :— 
ORDER. SECTION. FAMILY. GENUS, 
{ Branchiz in the mesial 
line, placed in a circle 
more or less complete 
around the anus. 
Liver compact......... Doripipz. 
Doris, Polycera, 
&e, 
Tritonia, Scyl- 
| the sides, or scattered. lea, Thetis. 
Branchie arranged cf 
L TRITONIADZ. 
NupIBRANCHIATA. 
branched or muricated, Dendronotus*, 
Branchie _ papillose, mf Dea Alderia, 
Eo.rpipz. Glaucus, &c. 
Liver disintegrated... 
Branchiz foliaceous. Acteon, Placo- 
AcTAONIDA. branchus ? 
EXPLANATION OF THE PLATES. 
Puate V. 
Fig. 1. Acton viridis, viewed from above. 
Fig. 2. The same, viewed in profile. 
Fig. 3. The head seen from below. 
Fig. 4. Vascular system: a a, trunks which receive the blood from the pos- 
terior parts of the branchial expansions; 6, circular vessel into 
which the trunks a a open, and which also receives the blood from 
the anterior part of the branchial expansions ; c, the ventricle. 
Puate VI. 
Acteon viridis opened from above; that portion of the hepatic ramifications 
which occupies the right side has been removed in order to sim- 
plify the figure, and for the same reason the ovaries? have not been 
represented on the left: a, buccal mass; b, tongue; c, canal through 
which the buccal mass opens exteriorly ; d, esophagus; e, stomach; 
Jf, intestine; gg, anterior pair of salivary glands; hh, posterior 
pair ; 2, pyriform sac opening into cesophagus; & #, anterior trunks 
of hepatic ramifications; //, posterior trunks; m mm, culs-de-sac 
in which the hepatic ramifications terminate ; ”, ganglionic collar 
of cesophagus ; 0, pharyngeal ganglia? ; p, optic nerve; g7, nerves 
running to tentacula and lips; s, nerves supplying the digestive 
system ; ¢, penis; v, oval cavity in base of penis; w, vas deferens; 
* I would feel well-inclined to separate Dendronotus as the type of a 
small family distinct from the true Kolidide. With Dendronotus | would 
also join Doto (Melibea, Johns.), and then the second section of Nudi- 
branchs would consist of three families, of which the Dendronotide would 
be exactly co-extensive with the subfamily Melibawine of Messrs. Alder and 
Hancock. With the animal assumed by Rang as the type of his genus Me- 
libea, I am not sufficiently acquainted to decide upon its exact location. 
Ann. & Mag. N. Hist. Vol. xvi. 
