238 SCIENTIFIC RESULTS OF THE 
liarly armed penis and by the imbedding in the pharyngeal bulbus of 
the buccal crop.! 
The Acanthodorides are not much depressed. The back is covered 
with soft villi or papille ; the openings for the rhinophoria have lobed 
margins. The gill is not retractile, and consists of several (generally 
seven to nine) tripinnate leaves, quite distinct from one another.” 
The labial disk is provided with a densely set armature of small 
hooks, passing backward on the cuticula of the mouth. This last also, 
in the lowest part of the mouth, at each side of the median line is 
thickened and projects like two thin, lancet-shaped blades over the 
bare space left between the lower parts of the prehensile collar... The 
form of the bulbus pharyngeus is as in the Lamellidorides, but the 
buccal crop is imbedded in the upper wall of the bulbus, opening into 
it through a slit, and is not conected with it by a short stalk. 
The tongue is not broad, but nearly fills the buccal cavity, with a flat 
furrow for the radula. This last has a naked rhachis, with a low and 
narrow, longitudinal fold. The pleure contain a very large, com- 
pressed, upright, lateral plate, with a large body and a rather short, 
strong hook, denticulated or plain along the inner margin; at the 
outer side of the large plate are several (four to eight) small, external 
plates (increasing in number backwards). The salivary glands long, 
thicker in their foremost part. The cesophagus with a little, crop-like 
diverticle at its root. Above the pyloric part of the intestine opens a 
1 The genus Calycidoris, of Abraham (Notes on some new genera of 
Nudibranchiate Moll., Ann. Mag. Nat. Hist., 4th ser., xviii, 1876, p. 182 ; 
and Revision of the Anthobranchiate Nudibr. Moll., P. Z.8., 1877, p. 224), 
which is said to be allied to the Acanthodorides and Lamellidorides, still 
differs by its ‘“‘subretractile’’ gill, with simple pinnate leaves, and does 
not possess external plates on the radula. The genus is very probably 
apocryphal ; in the phanerobranchiate Doridide it often happens that the 
gill appears as if more or less retracted in a cavity. A single new species 
is mentioned, of unknown habitat, the C. Guntheri, Abr., 1. ¢., p. 183, Pl. 
vis figs d. 
2 Alder and Hancock mention and figure (1. ¢., Pl. 15, fig. 2, 3) the 
branchial leaves as ‘‘ united at the base ;’”? so do Meyer and Moebius (I. c., 
p. 65); this is not the case. The leaves are quite isolated, but there are 
usually one or two foliola standing between them, which might simulate a 
coherence of the leaves (cf. also Pl. xv, fig. 6, A. and H.). 
3 These thickenings of the euticle have been regarded, both by Alder 
and Hancock, and more lately by Meyer and Moebius (1, c., p. 64, taf. v 
A, fig. 8, K 9), as “‘jaws,’’ but have hardly anything in common with those 
organs properly so called. 
