CHAPTER III. 



THE HABITS AND METAMORPHOSIS OF GONODACTYLUS CHIRAGRA. 



By W. K. BROOKS. 



(With PI. i, in, xiv, and xv.) 



THE STRUCTURE AND HABITS OF THE ADULT. 



This well-known species is found along the shores aud islands of all tropical and subtropical 

 sea, and our collections contain specimens from the Atlantic, the Pacific, and the Indian Oceans. 

 Among the many localities where its presence has been recorded the following may be named: 

 Bermuda, Florida Keys, Bahama Islands, Cuba, St. Thomas, Brazil, Mediterranean, Cape St. 

 Eoque, Samboanga, Samboanga Banks. Nicobars, Red Sea, Amboina, Indian Ocean, New Guinea. 

 It is subject to but little variation, notwithstanding its very wide distribution, and also notwith- 

 standing the fact that there are several other distinct species of Gonodactylus extremely similar 

 to cbiragra, aud distinguishable from it by only very minute differences. There is a well-marked 

 chiragra-like group of species all so close to each other that their divergence from each other must 

 have been comparatively recent, and in view of this fact it seems remarkable that one of these 

 species should so persistently retain its identity when exposed to such a wide diversity of 

 conditions. 



The species may be thus characterized : Stomatopoda with the sixth abdominal somite sepa- 

 rated from the telsou by a movable joint; the hind body convex; and the dactyle of the raptorial 

 claw without spines and enlarged at the base ; rostrum consisting of a transverse proximal portion 

 more than twice as wide as long, with subacute antero lateral angles and a slender, acute median 

 spine which does not quite reach to the bases of the eyes ; carapace nearly rectangular, three fifths 

 as long as wide, leaving the dorsal surface of the second thoracic somite completely exposed ; au- 

 tero-lateral angles semicircular and projecting beyond the median gastric area, which is nearly flat, 

 and bounded by two nearly parallel gastric sutures, which are continued to the posterior edge of the 

 carapace, which is nearly transverse with rounded postero-lateral angles; the transverse cervical 

 suture is faintly marked, distant from the anterior margin about two-thirds of the length of the 

 carapace; second thoracic somite, somewhat narrower than the carapace, with acute lateral angles; 

 the eight following somites equal in width and wider than the carapace; the third, fourth, aud 

 fifth thoracic somites about equal in length; the lateral margins of the third are straight, with 

 rounded angles, aud as wide as the dorsal portion ; the fourth is narrowed a little towards the 

 lateral edge, and the fifth still more so ; dorsal surfaces of the free thoracic somites and of the first 

 five abdominal somites smooth ; hind body convex ; all the abdominal somites have marginal lateral 

 cariuff, which are nearly linear, with the anterior end only a little wider than the posterior end; 

 postero-lateral angles rounded in the first four abdominal somites, rectangular in the fifth, aud 

 acutely pointed in the sixth; there are no dorsal carimB on the first five abdominal somites, and 

 no median dorsal carina on the sixth, which carries three pairs of swollen convex lateral cariiue, 

 which are equal in length and end posteriorly in acute spines, which are occasionally wanting 

 on the submediau pair; the external carina is much less swollen than the others, and it unites 

 at its posterior end with the laterial marginal carina; the spines of all the carinse project beyond 



the posterior edge of the somite aud lie in the same transverse plane. 



353 



S. Mis. 94 23 



