1880.] * NATURAL SCIENCES OF PHILADELPHIA. 89 



liarly armed penis and by the imbedding in the pharyngeal bulbus of 

 the buccal crop,^ 



The Acanihodorides are not much depressed. The back is covered 

 with soft villi or papillte ; 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 connected 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 pleuraj 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 oesophagus with a little, crop-like 

 diverticle at its root. Above the pyloric part of the intestine opens a 



' The genus Calycidoris, of Abraham (Notes on some new genera of 

 Nudibranchiate Moll., Ann. Mag. Nat. Hist., 4th ser., xviii, 1876, p. 132 ; 

 and Revision of the Anthobranchiate Nudibr. Moll., P. Z. S., 1877, p. 224 j, 

 which is said to be allied to the Acantlwdorides 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 ; iu the phauerobranchiate Dorididm 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. OuniJieri, Abr., 1. c., p. 133, PL 

 vi, fig. 1. 



■■' Alder and Hancock mention and figure (1. c, PI. 15, fig. 2, 3) the 

 branchial leaves as "united at the base ;" so do Meyer and Moebius (1. 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 PI. xv, fig. 6, A. and H.). 



' These thickenings of the cuticle 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. 

 7 



