;54 THE VOYAGE OF H.M.S. CHALLENGER. 



Clionopsis, 1 Troschel. 



1854. Cliopsis, Troschel, Beitriige zur Kenntniss der Pteropoden, Archiv f. Naturgesch., Jahrg. xx. p. 222. 



1855. Clio, Gegenbaur (jiars), Untersuckungen iiber Pteropoden und Heteropoden, p. 212. 

 1862. Clionopsis, Bronn, Die Klassen und Ordnungen des Thierreichs, Bd. iii. p. 645. 



Characters and Description as for the family Clionopsidse. 



The animals of this genus have been wrongly placed next to Clione by nearly all 

 zoologists. Since the organisation of Clionopsis has become better known (Boas and I 

 have independently worked at the subject, but Boas' researches have priority to my own), 

 it is evident that in some respects this genus comes nearer to Pneumonoderma ; but 

 it possesses some peculiar characters in which it differs as much from the Pneumono- 

 dermatidse as from the Clionidse. It must therefore be placed in another family, the 

 Clionopsidse, already established by Costa. 



The three species of this genus may be distinguished as follows : — 



Key to the Species. 



I. Animal of large size ; the posterior gill possessing four very distinct radiating crests. 



1. Radiating crests of the posterior gill without fringes, . . . Clionopsis krolini. 



2. Radiating crests with fringes, ...... Clionopsis grandis. 



II. Animal of small size, with the radiating crests on the posterior gill nearly obsolete, Clionopsis modesta. 



1. Clionopsis Jcrohni, Troschel (PI. II. fig. 9 ; PL III. fig. 1). 



1854. Cliopsis krohnii, Troschel, Beitriige zur Kenntniss der Pteropoden, Archiv f. Naturgesch., 



Jahrg. xx. p. 222, pi. x. figs. 2-4. 



1855. Clio mediterranea, Gegenbaur, Untersuchungen iiber Pteropoden und Heteropoden, p. 212, 



pi. iv. fig. 14. 

 1869. Triehoeyelus inediterraneus (larva), Costa, Osservazioni su taluni Pteropodi del 



Mediterraneo, Annuario del Mus. Zool. d. R. Univ. 

 di Napoli, Anno v. p. 46, pi. i. fig. 3. 

 1873. Clionopsis krohnii, Costa, Pteropodi della Fauna del Regno di Napoli, p. 25, pi. v. 



figs. 7-9. 



Body long and thick. 



Head small ; nuchal tentacles much projecting (this is the Gymnosomatous Pteropod 

 on which these appendages are the most developed). 



Foot. — Anterior lobes with posterior right angle, so that their posterior extremity 

 is neither free nor very projecting ; the folded tubercle on the posterior end of the 

 foot is not divided by a median longitudinal wrinkle. Fins rounded at their distal 

 extremity. 



1 From Clione, a Gymnosomatous Pteropod, and o\pi;, appearance. 



