564 SIR CHARLES ELIOT. 



of other families obviously related to Tntonia. These mostly show an advance in the 

 direction of the Aeolid type, but do not seem capable of arrangement in a progressive 

 series culminating in Aeolis, as most of them have marked peculiarities of their own which 

 are not found in Aeolis or other families. Such are the Lomanotidae, Dendronotidae, 

 Scyllaeidae, Bomellidae, Tethymelibidae, Phylliroidae, Hedylidae and Pleurophyllidiadae. The 

 first six of these are not represented in the present collections, which is somewhat remarkable, 

 as Melibe, Scyllaea and Bornella are all common in the Indo-Pacific. 



Fam. Pleurophyllidiadae. 



These are animals of a remarkable external appearance, which it is easier to recognize 

 than describe. The form is elongate — oval or tongue-shaped. The back is somewhat coriaceous 

 and bounded by a distinct mantle rim which extends beyond the foot. The dorsal surface 

 is marked with longitudinal stripes or tubercles. The head is distinct and divided from 

 the body by a space which may be conveniently called the neck. In front of this neck 

 is a tentacular shield, the corners of which are usually drawn out into points. Behind the 

 neck and immediately under the anterior margin of the mantle are two small perfoliate 

 rhinophores. In front of them are often a wart (caruncula nuchalis) or several papillae. 

 Except in Pleuroleura there is a branchial apparatus. Behind the head and underneath the 

 mantle a cleft runs inwards in which are set a number of branchial lamellae, and the sides 

 of the body underneath the mantle edge also bear another series of lamellae. The vent, 

 genital and renal openings are all on the right side. Jaws strong and denticulate. Radula 

 with a strong median tooth, cusped and denticulate. Laterals varying in form, denticulate 

 or not. Liver much ramified, sending branches to the back and sides, which penetrate into 

 the lateral lamellae. On the margin of the mantle are cnidopores, often visible to the 

 naked eye, from which cnidae can be emitted. The reproductive system is unarmed. 



The family appears to be cosmopolitan, but is recorded in especial abundance of species 

 from the Indian Ocean. The systematic position of the Pleurophyllidiadae has given rise 

 to some discussion. The older naturalists created a division, Inferobranchiata, to contain this 

 family, the Phyllidiadae and Hypobranchiata (= Corambe), but it is now generally admitted 

 that this association of forms is artificial and untenable. The presence of cnidae and the 

 ramification of the liver are points of connection with the Aeolids, and Pelseneer (Recherches 

 sur divers Opisthobr (inches, 1893) actually places the Pleurophyllidiadae among the Aeolidioidea. 

 But their dentition allies them to the Tritonids, and they have distinctive peculiarities which 

 separate them from both Aeolids and Tritonids. No connecting links have yet been discovered 

 which throw light on their relations to other groups. 



Gen. Pleurophyllidia Meckel'. 



PleurophyUidia possesses lamellae under the mantle both at the sides and in a cleft. 

 It is distinguished from the other genera which possess them by the following characters. 



1 Bergh, Bidrnri til en Monorir. af PleurophylUdierne, Kenntniss der Nudib. der brasilianischen Kiiste," Jahrb. d. 



1866. Id. S. R. VI. 1874. Id. Beitriiye zur Kenntniss der Malaco. Gesel. xni. 1886. Eydoux et Souleyet (under name 



Japanischen Nudibranchien, 1880. Id. Weitere Beit, znr Diphyllidia, Voyage de la Bonite, 1841). 

 Kemdniss der PleurophijUidien, 1890. von Jhering, " Zur 



