2 Rev. T. R. R. Stebblng on Antic Crustacea. 



BRACHYURA. 



Tribe O X Y Jt K ii y n c h a. 



Fam. Maiidae. 



Genus Hyas, Leach, 1813-1814. 



Ill/as araneiis (Linn.). 



17o8. Cancer aranetts, Liun., Svstema Xaturae, ed. x. (roprint, 1894), 



p. 628. 

 17i)0. Cancer biifo, Ilerbst, Naturg. Krabben u. Krebse, vol. i. pt 8, 



p. 242, pi. xvii. fig. 9o. 

 1814. Jli/as aranens, Leach, Edinb. Encycl. vol. vii. p. 4,31. 

 1816. Byas cnamus, Leach, Malacostraca Podophth. Britanniae, 



pi. xxi. A. 

 1834. Byas aranea, Milue-Edwards, Hist. Nat. Crust, vol. i. p. 312. 

 1851. Si/as aranetis, Brandt, Middendorfl's Sibirische Reise, vol. ii. 



pt. i. p. 76. 

 1853. Hyas arancus, Bell, British Stalk-eyed Crustacea, p. 31, fig. in 



text. 

 18(i4. Hyas aranevs. Goes, Crust, podcphth, Suecise &c., inCEfv. Vet.- 



Akad.'Forh. p. 161 (extr. p. 1). 

 1882. Hyas coarctatus, var., Iloek, Die Crustaceen des Willem 



Barents, in Nied. Arch, fiir Zool., Suppl. vol. i. p. 3, pi. i. fig. 1. 

 1887. Hyas araneus, II. J. Hansen, Dijmphna Krebsdyr, p. 234. 



]n regard to tlii.s abundant, widely distributed, and well- 

 known species tbere is still an unsettled question. Leach in 

 one work mentions and in another figures a specimen 

 measuring 16 inches across between the tips of the extended 

 legs. 1 he carapace of the specimen figured is .'^^ inches long 

 by a little over 2^ broad. These dimensions, as Leach 

 himself recognizes and as subsequent experience has shown, 

 arc very uncommon. From this form, capable of so large a 

 development, the same author in 1815 distinguished, as Hyas 

 ccarcfatus, a second species, of which a specimen is considered 

 fine when the carapace is 1^ inch long by | inch wide. Leach 

 did not, however, lay any stress on the difference in size, but 

 on a character less easily appreciable, namely, that the acute 

 lateral postorbital process of the carapace is tuberculate to the 

 rear in I/i/as araneus^ whereas to the rear in Hyas coarctatus 

 it is much dilated and unarmed. The latter species more- 

 over, in accordance with its name, has the sides of its carapace 

 constricted. It is not said, and it would not be true to say, 

 that they are without constriction in the other form. The 

 fact a])pears to be that the constriction forms a small pocket 

 (as in the smaller of Leach's two figures of Hyas coarctatus) 

 only in small specimens, but tliat, as specimens increase in 

 size, it becomes a shallow emargination. 



