36 A MONOGRAPH OF THE 



1st Sub-order. Anthrobranches. 

 1st Fam. 'Les Doris.' Doris, Onchidoris, Polycera. 



2d Sub-order. Polybranches. 

 2d Fam. c Les Tritonies! Tritonia, Doto, Thetys, Scyllsea. 

 3d Fam. 'Les Glauques.' Laniogera, Glaucus, Eolis, Tergipes. 



This is, in its essential points, the arrangement of the present day; very little alteration 

 having been made beyond the addition of the genera since discovered. The arrangement of 

 Blainville is that of Ferussac with an alteration of names. His orders " Cyclobr •anches" and 

 "Polybranches" are the two sub-orders above mentioned; and his families te Diceres" and Tetr acres, 

 in the latter order, correspond with the Tritonies and Glauques of Ferussac : these orders, 

 however, were placed nearly the last in a descending series. Rang added two new families, Les 

 Pterosomes and Les Placobr ancles : the former appears rather to belong to the Nucleobranchiata. 

 We find in the British Museum Catalogue for 1840, the Gymnobrancliiala {Nudihranckiatd) 

 comprises the following families : — 1, Dorida; 2, Tritonidte; 3, Placobranchidce; 4, Phyllidiadce; 

 5, Patellidcs ; 6, Chitonidm, The two latter families have been withdrawn in Dr. Gray's 

 subsequent arrangements, which we shall have to notice afterwards. M. D'Orbigny also 

 includes the Placobranchidce and Diphyttidiadce in his order Nudibranchiata published in 1842.* 



The next arrangement we shall notice is that of M. de Quatrefages (1844). In con- 

 formity with his views on the anatomy of these animals, he detached the JEolididce from the 

 Nudibranchiata, leaving that order to consist of the Dorididce and Tritoniadce alone, and 

 established a new order, Phleb enter ata, in which he includes the JEolididce, the Placobranchidce 

 of Rang, and a few small genera without special breathing organs, mostly new. His 

 arrangement of the order Phelebenterata is as follows : 



Gasteropodous Mullusca with an imperfect circulation or none, and without respiratory 

 organs properly so-called. 



Fam. 1. Intestine ramified, and prolonged into the external appendages. Enterobranches. 

 Tribe 1. Appendages isolated, more or less numerous. Enterobranches proprement dit. 



Eolide, Eolidine, Zepliyrine, Ampliorine, Calliopee, Cavoline (?), Glaucus (?), &c. 

 Tribe 2. Appendages united in the form of oars. Enterobranches remibranches. 

 Acteon, Acteonie, Placobranche (?), &c. 

 Fam. 2. Intestine very simple, in the form of a few pouches ; no external appendages. 

 Dermobranches. 

 Pavois, Chalide. 



In the first part of the present work (1845) we arranged the British species then known 

 in the following order : 



Fam. 1. Doridtd^e. Branchial plumes surrounding the vent on the medio-dorsal line. 

 Sub-Fam. Doridince, with a cloak. 



Doris, Goniodoris, Triopa. 

 Sub-Fam. Polycerinae, without distinct cloak. 

 iEgirus, Thecacera, Polycera, Idalia. 

 Fam. 2. Tritoniad^e. Branchiae, laminated, plumose or papillose, arranged down the sides of 

 the back; stomach entire. 

 Tritonia. 



* In his ' Paleontologie Francoise.' 



