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g. Hynicniciis marmoratus Chilton. 



1881. Hynienicus marmoratus Chilton. Transact. Proc. N. Z. Inst., v. 14, p. 172, pi. 8, f. i 

 (2J and 3^1 maxilliped, abdomen). 



It is to be regretted that Chilton does not give ample information about this species, 

 said to be common in Lyttelton Harbour (New Zealand). It is closely allied to H. varius, but 

 differs in having the carapace subtriangular, not circular, the two pairs of teeth at the antero- 

 lateral margins being conspicuous, not obsolescent. 



Rhynchoplax Stimpson. 



1858. Rhynchoplax Stimpson. Proc. Ac. Nat. Sc. Philadelphia, 1858, p. 109. 

 1900. Hynienicus Alcock. Journ. As. Soc. Bengal, v. 69, prt 2, p. 387. 

 1907. Rhynchoplax Stimpson. Smithson. Inst., Miscell. Coll. vol. 49, p. 147. 



The sharp three-spined rostrum distinguishes this genus in my opinion sufficiently from 

 Hynienicus, to which it was united by Alcock. Rhynchoplax is apparently essentially tropical, 

 but at the south-east coast of Australia the genera may occur together. 



The following may serve to distinguish the 7 species, referred by me to the present genus : 



1. Rostrum consisting of only one long spine between the eyes, and at 



either side of the base with an obscure tooth; eye-stalks long, 

 reaching as far as the much prominent external orbital angle ; 

 penultimate peduncle-joint of the antennules reaching as far as 

 rostrum ; antero-lateral margin of carapace with 3 teeth at either 

 side. Wrist of cheliped with 3 short, elevated, longitudinal carinae; 



palm acute above and below R. rostra ta (Haswell) 



Rostrum consisting of three spines between the eyes. Wrist of 

 cheliped without ridges 2 



2. No teeth (at most a faint prominence) at antero-lateral sides of cara- 



pace; median spine of rostrum somewhat longer than lateral ones 3 

 Lateral sides of carapace with one or more pairs of teeth ... 4 



3. Length of carapace (including rostrum) equal to breadth; walking" 



legs about twice the breadth of the carapace R. krefftii (Hess) 



Length of carapace (including rostrum) much exceeding breadth ; 

 walking legs longer than 3 times the breadth of the • carapace ; 

 median spine of rostrum Yj the length of the rest of the carapace. 

 Meropodite of cheliped with a subdistal tooth at outer border . R. inacJioides (Alcock). 



4. Antero-lateral margins of carapace with more than one pair of teeth. ' 



Meropodite of cheliped toothed at distal end of outer or upper 



border 5 



Antero-lateral margins of carapace with only one pair of teeth; 

 rostrum consisting of a long median and two short lateral spines. 



Meropodite of cheliped unarmed - R. coralicola Rathbun 



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SIBor.A-EXPEDITIE XXXIXc. -- 3 



