MARINE CRUSTACEANS. 



VIII. STOMATOPODA, WITH AN ACCOUNT OF THE VARIETIES 

 OF GONODACTYLUS CHIRAGRA. 



By W. F. Lanchester, M.A., King's College, Cambridge. 



(With Plate XXIII.) 



I. ADULT forms; 



The adults in this collection all belong, with the exception of two specimens of 

 Pseudosquilla ciliata, to the genus Gonodactylus ; moreover they should be included in a single 

 species of that genus, namely, the world-wide G. chiragra. On first being sorted out these 

 Gonodactylus fell fairly readily into three groups, (a) representing the G. chiragra of most 

 authors (not of Fabricius, to which point I shall return later), {h) representing the G. glabrous 

 of Brooks, and (c) seven specimens representing the G. spinosus of Bigelow. Closer examina- 

 tion, however, revealed in each of the first two groups a considerable amount of variation, 

 chiefly in respect to the characters of the 6th abdominal segment and the telson, that is 

 to those which more particularly distinguish the two forms : and in seeking to group these 

 variable forms I was led insensibly to the conviction that no hard-and-fast line could be drawn 

 between the two species, and that Brooks was right in his estimate, which I did not see 

 till later, that " future discoveries may reveal so many transitional forms that the shaip lines 

 between the species" (including a third, the G. graphiirus of Miers) "will break down" (Chall. 

 Stom. p. 64). The third group, that of G. spinosus, numbers but few specimens, and therefore 

 presents little evidence of variation. 



The great preponderance of this species in the Maldives and Laccadives is a striking 

 fact, for which, unfortunately, no explanation can at present be forthcoming. A partial 

 explanation lies in the fact that these forms are found on the surface of the reefs, or sea- 

 bottom, whereas the genus Squilla, so conspicuous by its absence in this region, and yet 

 one of the commonest forms of Stomatopods in the Indo-Malaysian region, lives in burrows 

 in the sand or mud, from which it is a matter of some difficulty to dig it out even when 

 the burrows are uncovered at low water, while it renders it unlikely that many will fall 

 victims to the dredge. But this is only the smallest part of the question; for Mr Stanley 

 Gardiner has assured me that he used every effort to obtain Squilla from holes at low 

 water, so that we may feel certain that, had the genus existed in any quantity at all, 



