4 MR MACDONALD ON THE ANATOMY 



I had originally intended to pass all the genera in review, dealing with the 

 whole anatomy of each in the order observed in the foregoing table ; but this 

 would extend the paper beyond reasonable limits, and perhaps prove monotonous 

 to the reader, from the frequent repetitions of essentially the same anatomical 

 particulars, however striking their modifications may be, in the different members 

 of this natural order. 



I shall therefore first make selection of Firoloides a.ud Atlanta for especial 

 description, occupying, as I conceive them to do, the two extremes of the group ; 

 and those modifications to which I have alluded may be briefly noticed in a 

 passing glance at the remaining genera, or at least the particular species which 

 have casually fallen under my observation. 



Firoloides (Lesueur). 



While cruising in the South Seas, and subsequentlj^ in the neighbourhood of 

 the West India Islands, I was fortunate enough to obtain numerous specimens of 

 a solitary species of Firoloides, and which I find, if I am not very much mistalcen, 

 has been several times named by different writers who may have met with it 

 under such deceptive conditions as to mask its identity. Thus, the male and 

 female of this species are represented in Plate XVL, Voy. la Bonite, figs. 8 and 1 

 respectively, though the former has been designated Firola de Keraudrew, as also 

 Eydouxii, and the latter F. de Desmarest. I have traced it, moreover, under other 

 names in certain less definite figures, illustrating the works of the French natur- 

 alists, who appear to have had most to do with the Heleropoda from the very 

 foundation of the order, though it is scarcely reconcilable with Lesueur's figure 

 of Firola Demerastiana (1, c, i, 39, t. 2, f, 1 ), which Dr Gray seems to regard as 

 the type of the genus Firoloides. Now, though all this may be justly regarded as 

 a stumbling-block to the student, he has still more to encounter in the literature 

 of other genera. I shall therefoi-e eschew the naming mania altogether, and 

 simply attempt succintness of description, aided by fidelity in the figures, so as to 

 render the species in question just as definite as if I were to add fresh synonyms 

 to the existing confusion. It is a cheering reflection, however, to know that we 

 have in the lingual dentition a guide that cannot be gainsaj'ed, and whose ex- 

 punging power may be safely applied to a host of w??.9-applied cognomina with 

 their bracketed italics. 



On entering Bass' Strait in H.M.S. "Torch," I obtained my first Firoloides., 

 which was so perfectly transparent that, but for the brilliancy of its eyes, relieved 

 by the dark pigment coat protecting the retina3, it would probably have passed 

 unobserved. When immersed in sea-water, the eyes were seen rapidly swaying 

 from side to side with the undulatory movement of the elongated and pliant body, 

 no other parts being visible but the faint]}'^ rose-tinted visceral nucleus and the 

 little buccal mass. 



