HYMENOSOMIDAE. 



Since the arguments put forth by Ortmann ^) and Borkadaile -), it is now generally 

 agreed, that the present family is to be classed with the Oxyrhyncha, and not with the 

 Catometopous Crabs; indeed, the only character that may justify the latter view, viz. the sternal 

 openings of the cT sexual organs, is counterbalanced by a whole series of features showing a 

 close relationship to the Oxyrhyncha and especially to the Maiidae. It is remarkable, that 

 DE Haan ^), as early as 1839, referred his species "" Ocypode (Elamene) iinguiformis\X.o the 

 "Majacea"; in the atlas the species is called '^ Inachus (Elamene) uiiguiformis\ 



The Hymenosomidae are all littoral species ; in the very rare instances, that they are 

 found in the open sea, they seem to be clinging to some floating object. The majority of 

 species inhabit the waters of New Zealand and the south and east coast of Australia ; from 

 here they radiate towards the Indian Ocean, to China and Japan, to New Caledonia and the 

 west coast of South America, and to South Africa. One species is characteristic o( sub- 

 antarctic regions. 



It is to be regretted, that most of the species are very insufficiently known, and it has 

 been put forth by several authors, that a thorough revision, especially of the New Zealandian 

 species, is much needed. Even the genera are not well defined, so that it has appeared advisable 

 to some carcinologists to unite all the known forms into one single genus, Hymenosoma. 



Under these circumstances it is a difficult and ungrateful task to undertake a systematic 

 monograph of the present family. Nevertheless, with the scanty material of the "Siboga" added 

 to some few, but interesting specimens of the Leyden and Amsterdam Museum *), I am of 

 opinion that even the description of this small collection, the defining of genera and eventually 

 of species, and the compilation of the literature, incomplete as this modest monograph appears, 

 may be of some use to any one who chances to examine any members of the present family. 



1) Zool. Jahrb., Syst., Bd 7, 1894, p. 31. 



2) Fauoa and Geogr. Maldive and Laccadive Arch., v. 2, 1903, prt 2. Marine Crust. X (Oxyrhyncha) p. 682 (note). — Ann. 

 Mag. Nat. Hist. (7) v. 19, 1907, p. 480. 



3) Fauna Japonica, dec. quarta, 1839, p. 75, pi. 29, f. I. 'I)pM' 



4) Prof. Weber has Icindly allowed me to insert the descriptions of these specimens from the said Museums, for, though not 

 caught by the "Siboga", they are Indo-Pacific as well. 



