REPOET ON THE PTEEOPODA. 43 



the necessity of forming new genera for some Gymnosoniatous forms which I consider 

 undoubtedly to belong to the genus Clione. 



Gegenbaur, indeed, unfortunately confounding the tentacles and buccal appendages 

 under the same name, divided Clione into two groups 1 : — (1) those with more than two 

 "tentacles" — " Clio borealis" and " Clio australis"; (2) those with two tentacles — " Clio 

 cajoensis, Clio longicaudata, Clio limacella, Clio jlavescens, and Clio mediterranea " ; and 

 he says that if he had treated the question from the systematic point of view, he should 

 have created a new genus for these last species. 



But there are two species among these which do not belong to the family Clionidse, 

 namely, Clio capensis, Rang ( = Notobranchiea sp.), and Clio mediterranea, Gegenbaur 

 ( = Clionopsis hrolvni, Troschel). "Clio" longicaudata, Souleyet, besides its true 

 tentacles, which number two pairs as in Clione limacina (=Clio borealis), possesses 

 two pairs of buccal cones of the same nature as the three pairs in the latter species. 

 Clio limacella, Rang (which has never been described, but only figured), is a species very 

 closely allied to Clione longicaudata, if not identical with it, and it very probably also 

 possesses two pairs of buccal cones. Finally, respecting " Clio " Jlavescens, Gegenbaur, 

 we shall see further on that our knowledge of its larva shows that it also possesses two 

 pairs of buccal cones, as in Clione longicaudata. Thus, these latter species do not differ 

 from the type of the genus Clione, except by having two pairs of buccal cones instead 

 of three ; and I think that this difference is not at all a generic one. 



Macdonald also thought that one might generically separate the forms with three 

 pairs of buccal cones from those which only possess two. 2 In his group with two pairs of 

 buccal appendages, Macdonald includes two forms ; one very close to Clione longicaudata, 

 the other with a posterior gill, which thus does not belong to the family Clionidas, 

 and which must be removed from the Clione with two pairs of buccal appendages 

 as well as from those which possess three pairs, and will be placed in the genus 

 Notour anchsea. 



It is quite as inadmissible for me to generically separate forms of Gymnosomata so 

 nearly resembling one another, because they have two or three pairs of buccal cones, as 

 to place in the same genus a Gymnosomatous Pteropod with a gill (Notobranchsea) and 

 another without a gill [Clione). All the Gymnosomata with an elongated body, without 

 a gill and with buccal cones (two or three pairs), must be placed in a single genus 

 Clione. 



Lastly, Fol, on account of the species he has called " Clio " aurantiaca, also thought 

 that he should establish a new genus. 3 As we shall show further on, " Clio " aurantiaca 

 must be considered as the old larva of a previously known species of the genus Clione. 



1 Untersuchungen iiber Pteropoden und Heteropoden, p. 2] 2. 



2 On the Zoological Characters of the living Clio caudata, Trans. Roy. Soc. Edin., vol. xxiii. p. 187. 



3 Sur le developpement des Pteropodes, Archives d. Zool. exp^r., ser. 1, t. iv. p. 172. 



