92 A HISTORY OF RECENT CRUSTACEA 



rhomboides (Linn.), called in Bell's ' History of the 

 British Crustacea' Gonoplax mjiiluta (Fabricius), the 

 angular crab, the specific name obviously, and the generic 

 name probably, alluding to the angular character of the 

 carapace. A second species, closely resembling the first, 

 and named Gonoplax sinuatifrons, Miers, was obtained by 

 the Challenger at Amboina. The elongated orbits and 

 eye-stalks cannot fail to attract attention, and the latter 

 especially when they ai-e suddenly erected from a position 

 of rest within the former. The male has the chelipeds of 

 a remarkable length, and these, at least when in confine- 

 ment, he is fond of clashing together in a noisy and 

 perhaps threatening manner. The joints of these limbs 

 are so proportioned that while they are able to seize food 

 at a great distance, they can also convey it to the mouth. 

 The pleon is seven-jointed in both sexes. 



OmmatocarclnuSj White, 1852, is distinguished from 

 its near neighbour Gonoplax by a still narrower ' front,' a 

 great development of the antero-lateral spine on each side 

 of the carapace, and still more elongate eye-stalks, to 

 which reference is made in the generic name, meaning 

 ' the crab with the eyes.' There is but one species, Omma- 

 tocarcinus Macgillivrayi, White. This is found in Austra- 

 lian and New Zealand waters. 



MacropJithalmus, Latreille, 1829, with a name mean- 

 ing ' long-eye,' surpasses the two preceding genera in the 

 length of the orbits, and the eye-stalks are exorbitant in 

 the literal sense in certain species, in which they are pro- 

 longed laterally beyond the orbit's outer angle. The 

 species are numerous, occurring ' in the littoral or shallow 

 waters of all parts of the Indo-Pacific region.' In some of 

 the species, as also in the genera Hellce, de Haan, 1835, 

 and Metaplax, Milne-Edwards, 1852, the males have on 

 the arms of the chelipeds a short horny ridge, which Dr. 

 de Man calls ' the musical crest,' on the supposition that 

 the crab produces musical sounds by rubbing this crest 

 against a row of granules below the orbit. Naturally 

 this crab-music must only be judged by a crustacean 

 standard. 



