258 [No. 4, 



Oif A New Get^us and Species {Hylceocarcinus ILumei) of Landcrabs 

 FROM the Nicoear Islands, — hij Jas. Wood-Mason, of Qiceeri's 

 College^ Oxford. 



(With Plates XV & XVI.) 

 (Received aud read August 6th, 1873.) 

 Milne-Edwards, in his classical work on the entire class of Crustacea 

 published in 1837, divides* the four then recognized genera of the small but 

 remarkable group of Gecarcinidce, or Landcrabs properly so-called, into 

 two divisions accordingly as they have the terminal joints of the external 

 maxillipeds completely exposed, or inserted on the internal face of the third 

 joint near its summit and completely hidden beneath it ; and Danaf in his 

 great work not only adopts these divisions but gives them subfamiliar 

 names : — '' The QecarcinidcBj^ he says, " pertain naturally to two groups 

 or subfamilies, one having the termination of the outer maxillipeds exposed 

 as usual, the other having this part concealed beneath the second and 

 third segments. The subfamilies and genera are as follows : — 



Sttbfam. 1. UCAIN^. Articulus maxillipedis externi 4tus apertus. 



1. Maxillipedes externi non liiantes. 



G. 1. UcA, Leach. Articulus maxillipedis externi ditus angulo extern o 

 insitus. 



G. 2. Gecaecintjcus, Edwards. Articulus maxillipedis externi 4tus 

 marginis medio apicalis 3tii insitus. 



2. Maxillipedes externi late liiantes. 



G. 3. Cabdisoma, Latr, Articulus maxillipedis externi 4tus apice 3tii 

 externo insitus. 



G. 4. Gecarcoidea, Edwards. Articulus maxillipedis externi 4tus 

 marginis medio excavato apicalis 8tii insitus. 



SuBFAM. 2. GECARCININiE. Articulus maxillipedis externi 4tus et 

 sequentes 3tio celati. 



G. 1. Gecarcinus, Latr, 



This division is unnatural as separating the genus Gecarcoidea (hodie 

 JPelocarcinus) from Geca7^cinus to which it is most closely related, and 

 ranging it with others with which its relations are more general ; and the 

 classificatory value of the character upon which it is based is, moreover, 

 much diminished, if not altogether destroyed, by the discovery of a new form 

 presenting an interesting transition from the former to the latter genus in 

 this very character. A more natural result can, however, be attained, and 



* Hist. uat. des Crust., Vol. II, p. 20. 



t Unit. States Expl. Exped., Crust., Vol. I, pp. 374-375. 



I 



