152 Memotrs of the Indian Museum. [VOr.cEV 
numbers already in use, the term variety being restricted to such cases as conform with 
Borradaile’s definition. 
Turning to the forms that differ from G. chivagra in characters of a more trenchant 
nature, intermediates being rare or perhaps wholly absent, the first that must be con- 
sidered is Wood-Mason’s Gonodactylus platysoma. No description of this form has ever 
appeared and its claim to recognition rests solely on the figures published in 1895. 
G. platysoma may be distinguished from G. chivagra by its broader form and by the size 
and shape of the terminal part of the raptorial dactylus. ‘The telson, with its narrow 
carinae and complete absence of lateral teeth on the margin differs markedly from that 
of any G. chiragra in the collection ; but in this respect the form bears a close resem- 
blance to certain examples to which Lanchester gave the name of G. chiragra var. acutus, 
and it is possible that these specimens are identical with those determined by Wood- 
Mason. Judging from the material in the Indian Museum G. platysoma seems quite 
sufficiently distinct from G. chivagra to claim recognition as a variety. 
In Atlantic waters G. chivagra is represented by a form known as G. oersted?, 
Hansen, which differs from its Pacific relative in the possession of a small additional 
keel on the inner face of the intermediate teeth of the telson edge. ‘The character is so 
trivial that for many years it entirely escaped detection, but it seems nevertheless to 
prevail with the most absolute constancy. I have followed the general consensus of 
opinion in regarding this form as a distinct species, but some may consider subspecific 
rank more suitable. 
When describing Gonodactylus acutirostris, Dr. de Man mentions that it is possibly 
only a variety of chivagra; but, though it is true that it may eventually prove to be a 
very abnormal form of that species, it should remain separate pending further informa- 
tion. In the single known example the antero-lateral angles of the rostrum are much 
more acutely produced than in any G. chivagra,' and on the dorsal surface of the telson 
the two small tubercles, that are situated close to the anterior margin in all the allied 
forms, are entirely absent, while the submedian carinae are posteriorly convergent. 
I have seen no specimen possessing any one of these characters. 
Gonodactylus demant, Henderson, and spinosus, Bigelow, are forms which are dis- 
tinguishable at a glance from all the preceding by the presence of spinules on the dorsal 
surface of the telson. Apart from this feature G. demani bears a close resemblance to 
G. chiragra, from which, however, it may be separated by the shape of the dorsal pro- 
cesses of the ophthalmic somite and by the height and extreme convexity of the mid- 
dorsal lobe of the telson when seen in lateral view. The dorsal aspect of the telson 
presents, moreover, a very distinct and characteristic facies, for the three dorsal keels, 
and those which terminate in the submedian and intermediate marginal teeth, are all 
strongly swollen, and are separated from one another by narrow \j-shaped grooves that 
form a striking contrast to the comparatively wide interspaces found practically with- 
out exception in G. chiragra. Lanchester, strangely enough, does not mention this 
form in his synopsis of the varieties of G. chivagra; he has in fact omitted all reference 
to it, though he cites the paper by Henderson that contains the original description. 
' But there is, indeed, no little variation in G. chiragra in this respect. 
