12 
THE VOYAGE OF H.M.S. CHALLENGER. 
recognition, either through the inadequacy of the descriptions or the rough inaccurate 
character of the figures which are supposed to represent them. Of the first four species 
described, Pterotrachea coronata, Pterotrachea pulmonata, Pterotrachea aculeata, and 
Pterotrachea liyalina of Forskal, only the first has since been recognised. Even the 
figure of that species is extremely crude and fanciful. Nothing is known of the three 
others beyond the information given by Forskal, and since this is so incomplete and the 
figures so bad, I think it would certainly be advisable to reject these so-called species as 
beyond recognition. 
The next to describe some species belonging to this genus was Lesueur, who in 1817 
published short diagnoses and figures of six so-called new species, which he separated on 
account of the presence or absence of a fin-sucker, the want or possession of the caudal 
appendage, and the number of “ gelatinous points ” or denticles in front of the eyes. 
The stability of these species has been doubted by d’Orbigny and others, and it 
seems to me probable that in three or four instances only varieties or different sexes of 
the same species are depicted. Quoy and Gaimard and Risso have also described and 
figured species which probably will never be recognised, and of several other forms 
nothing is known except the original figures and descriptions, some of which evidently 
are inaccurate and incomplete. Still, as it is impossible to relegate them with absolute 
certainty as synonyms of well-recognised forms, I think it best to let them stand as 
separate species until it can be shown beyond a doubt what their true position is. It is 
dangerous to deny or doubt the existence or value of a species because we do not happen 
to have had the opportunity of examining or possessing an example. Although we may 
feel most confident that a certain so-called new species is either identical or merely a 
variety of some well-established form, still we are not warranted in “ sinking” an author’s 
species (as is often done by certain writers) upon mere suspicion. It is an injustice, and 
creates endless confusion in the nomenclature. 
In the following list the species are not arranged in the order of their apparent 
affinity, but merely according to priority of date of publication : — 
Pterotrachea coronata , Forskal. 
1775. Pterotrachea coronata, Forsk&l, Descript. Anim., p. 117. 
1776. 
99 
99 
id., leones, p. 10, pi. xxxiv. fig. A. 
1789. 
99 
99 
Gmelin, Svst. Nat., p. 3137. 
1791. 
9 9 
99 
Bruguiere, Ency. Meth. , pi. Ixxxviii. fig. 1 (copy of ForskSl). 
1801. 
99 
99 
Lamarck, Syst. Anim., p. 61. 
1805. 
99 
99 
Roissy, Hist. Nat. (Suite k Buffon), vol. v. p. 79. 
1822. 
99 
99 
Lamarck, Anim. sans Vert., vol. vii. p. 676; ed. 2, vol. xi. p. 383. 
1826. 
99 
99 
Risso, Hist. nat. Europ., vol. iv. p. 28. 
1829. 
99 
99 
Chiaje, Mem. Stor. Anim. senza Vert., vol. iv. pp. 182, 197. 
1830. 
99 
99 
Bose, Hist, nat., vers, ed. 2, vol. i. p. 64. 
