50 THE VOYAGE OF H.M.S. CHALLENGER. 



The following considerations clearly prove that this form is the young state of Clione 

 Jlavescens : — 



1. The presence of but one true Clione in the Mediterranean has been so far 

 ascertained, viz., Clione Jlavescens. On the other hand, only one larva of a true Clione, 

 " Clio aurantiaca," is known to exist in the Mediterranean. This form is indeed a 

 true Clione, a fact made evident by the shape of the foot, as well as by that of the 

 buccal appendages. As to the larvae of Clione described by Johannes Midler, 1 they 

 are identical with " Clio aurantiaca," as may be seen from the buccal appendages and 

 the radula. 



2. Clione jlavescens has never been collected except at Messina. At Messina also, 

 and there alone, the larva called " Clio aurantiaca" has been twice caught. 



3. Clione Jlavescens is yellow ; this also is the colour of " Clio aurantiaca." 



I therefore think there can be no doubt at all as to the identity of these two forms, 

 and hence one may safely conclude that Clione Jlavescens possesses two pairs of buccal 

 cones or cephaloconi, as exist in Clio aurantiaca. 



I cannot figure this species nor the foregoing one, because the only known 

 specimens do not now exist. They and Dexiohvanclisea •paucidens are the only species 

 that I have not myself seen. 



Among the species of the genus Clione which are imperfectly known, there are two 

 which in their general aspect rather closely resemble Clione longicaudata ; they are : — 



1. " Cliodita fusiformis," Quoy and Gaimard, 2 collected between the Cape of Good 

 Hope and Mauritius. 



2. " Clio limacella" Rang, 3 without description or recorded habitat ; only known 

 from figures. 



A Clione from the South-West Pacific, of which Dr. Macdonald gave me an original 

 drawing, very much resembles " Clio" limacella, and is of the same length (6 mm.) ; 

 they are both adults, because they no longer show any trace of ciliated rings. 



Lastly, " Clio " caudata, Macdonald, 4 which this writer identifies with Clione longi- 

 caudata, 5 also resembles very much " Clio " limacella. " Clio caudata," Macdonald, 

 which was collected off Sydney Harbour, possesses a radula of which the formula is 

 6 : 1 : G, and bears two pairs of buccal cones. 



Probably " Clio" fusiformis and " Clio" limacella are also provided with two pairs 

 of buccal appendages, and belong to the group of Clione longicaudata. 



Our knowledge of these species shows that the genus Clione is distributed south of 



1 Archivf. Anat. u. Physiol, p. 70, 1854. 



2 Description de cinq genres de Mollusques, Ann. d. Sci. Nat., sir. 1 , t. vi. p. 74, pi. ii. figs. 3, 4. 



3 Histoire naturelle des Mollusques Pteropodes, pi. x. figs. 10-12. 



4 On the Zoological Characters of the living Clio caudata, Trans. Roy. Soc. Edin., vol. xxiii. p. 185, pi. ix. fig. 3, 1. 



6 I cannot confirm this identification, because Macdonald gives no description of this form, and especially no 

 indication of the conformation of the foot. 



