jan. — mar. 1857.] Pelagian Mollusca collected, 8fC, 147 



II. Brief notices of Pelagian Mollusca collected on a voyage 

 from England to Madras, during the months of April, May 

 and June 1856. By William Traill, m. d. 



In throwing together the following observations it was my first 

 intention to describe the various Mollusca met with, in the order 

 of their classification, beginning with those highest in the scale, 

 but on further reflection I did not think it would answer any useful 

 purpose to do so. They are too few in number to represent the grada- 

 tion of the different classes,which may be more clearly understood by 

 a glance at any systematic work on the subject. By adhering rigidly 

 to classification I should have very frequently, to reverse the suc- 

 cession of events. Moreover, authors are by no means agreed as to 

 the exact position in the animal economy, which each group should 

 hold : Pteropods for example according to the varying opinions 

 of different authors, having successively occupied no less than three 

 of the six Classes into which MOLLUSCA are usually divided. 

 Upon the whole therefore, I thought it better to note down zoolo- 

 gical facts and deductions in the order of their occurrence as be- 

 ing a method easier to myself and probably more intelligible to my 

 readers. 



In remarking on these animals, I have not been so much actu- 

 ated by the belief that some of the species are new to science, 

 as by the fact that Pelagic Molluscs in general, and Pteropods in 

 particular, are comparatively little known. Although the indefati- 

 gable labours of such men as M. M. Bang, Quoy and Gaimard 

 have greatly added to the number of ascertained species, yet in our 

 knowledge of their specific distinctions and affinities much remains 

 to be accomplished. 



Pteropods are rarely seen either in public museums or private 

 collections ; their mysterious haunts in the unknown depths of the 

 ocean render them peculiarly inaccessible to the majority of col- 

 lectors ; even the experienced voyager, without some previous know- 

 ledge of their habits, would fail to detect any indication of their 



