1900.] FROM THE FALKLAND ISLANDS. 525 



1885. Halicardnus planatus, Filhol, Recueil de Mem., Exp. pass, 

 de Venus, Zool. p. 396. 



1886. Halicardnus planatus, Miers, ' Challenger ' Brachyura, 

 Reports, vol. xvii. p. 281. 



From what has been said on the genus it will be understood that 

 the mere record of H. planatus is no very certain guarantee that 

 precisely this species was obtained in the locality assigned. In the 

 works of Fabricius and Herbst above mentioned, between 1775 and 

 1793, a species named Cancer orbiculus from New Zealand takes 

 precedence of the Fuegian Cancer planatus. 



Miers in 1876 says : " The type specimen of the C. orbiculus of 

 Fabr. is in the Collection of the British Museum. It is very much 

 injured, but 1 think it can be nothing but a specimen of H. plan- 

 atus with the marginal teeth obsolete." He does not, however, 

 endorse his opinion by substituting the name orbiculus for planatus, 

 and this is prudent, unless the state of the specimen permits of its 

 being distinguished, for example, from Hymenicus varius Dana, 

 which also comes from New Zealand and is without teeth to the 

 carapace. 



In the following notes on specimens brought by Mr. Vallentin 

 from the Falklaud Islands, which specimens I take to be with 

 little doubt H. planatus, I propose to compare with them specimens 

 from Jervis Bay in Australia, sent to me by Prof. Haswell, 

 unnamed, but agreeing in my opinion with H. ovatus Stimpson 

 (Plate XXXVI a.). 



In regard to the upper surface, there is a general agreement that 

 in the latter species the frontal margin is narrower and the teeth 

 of the tridentate depressed rostral projection more closely approxi- 

 mate than in the former. In both species the teeth are setiferous. 

 Of the marginal teeth the hinder, which is much the more pro- 

 nounced, is more setose in H. planatus ; and in this species, as Miers 

 notices, the carapace is much more hairy in some instauces than in 

 others, but tbat variability, for aught we know, may belong to 

 other species of the genus, or even be an incident in the life of the 

 individual. In front of the epistome there is, so far as I can make 

 out, a similar median septum in both species. In both the eyes 

 and antennae agree, unless it may be that the eyes in H. ovatus are 

 apically a little narrowed. The second anteunae have in both the 

 narrow peduncle much shorter than the stout one of the first ; while 

 Guerin in his Hymenosoma leachii describes and figures them as being 

 nearly equal in length. 



The mouth-organs are practically the same in both species, aud 

 their characters are sufficiently shown by the figures. The ex- 

 ternal or third maxillipeds of H. planatus are on the outer surface 

 of the third and fourth joints much more setose than those of 

 H. ovatus, and there are small but trivial differences in the outline 

 of the fourth joint. In the three terminal joints, both species 

 have numerous finely pectinate spines on or projecting from the 

 inner surface, which is shown in the figure. All three maxillipeds 

 have a long narrow epipodal lamina, and the transversely placed 



Peoc. Zool. Soc.— 1900, No. XXXV. 35 



