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XVII. — On the Zoological Characters of the Living Clio caudata, as compared with 

 those of Clio borealis given in Systematic Works. By John Denis Macdonald, 

 R.N., F.R.S., Surgeon of H.M.S. " Icarus." Communicated by Professor 

 Maclagan. (Plate IX. fig. 3.) 



(Read 5tli January 1863.) 



Great credit is due to those observers who have been enabled to give to 

 science both clear and comprehensive views of the anatomy of creatures which 

 have only been presented to them in a spirit-preserved, opaque, brittle, and con- 

 tracted state ; for it is certain that their penetration in this respect could not be 

 successfully brought into exercise without the aid of much knowledge, both 

 bibliographical and practical. Yet there are many whole animals, and, in par- 

 ticular, parts of animals, which must be seen in the living state, to be at all 

 comprehended by even the most brilliant mind ; and this fact has induced me 

 to make drawings and notes of many interesting matters connected with the 

 pelagic mollusca, when the living animals fell casually under my own observa- 

 tion. In the present communication, however, I shall confine myself to the 

 genus Clio. 



Good figures are in general more valuable than even lengthy descriptions ; 

 for though it would not be very easy to make a good figure from an imperfect 

 description, a very excellent description may be formed from an indifierent figure. 

 On consulting all the figures of Clio available to me, I found most of them far 

 short of nature, and all quite incapable of affording a just conception of the 

 living and fully expanded animal ; nor, indeed, can I say that any descriptions, of 

 the members of the genus extant answer much more than the purpose of mere 

 recognition, in a popular sense. 



In the widest sense of the word, the physiognomy of Clio caudata, in the 

 expanded state, is as remarkable as that of any animal in creation. The 

 head, or that enlargement in front which is separated from the body by a shght 

 cervical constriction, is fronted on either side by two small tentacula, one of 

 which has been supposed to be an eye pedicle, though there is no proof that Clio 

 enjoys one whit more visual faculty than any other Pteropod. Cuvier remarks, 

 that " some have asserted the existence of eyes ;" and subsequent writers say 

 that those in Clio, though minute, have a very complete organization. For my 

 own part, however, I cannot say that I have ever been able to detect them, 

 though I should be sorry, on this ground alone, to affirm that they are not pre- 

 sent. But the little tentacula just noticed are quite insignificant, in comparison 

 VOL. xxiii. part it. 3 f 



