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Show 1900.] PROM THE FALKLAND ISLANDS. 525 1885. Halicarcinus planatus, Filhol, Eecueil de Mem., Exp. pass. de Venus, Zool. p. 396. 1886. Halicarcinus planatus, Miers, ' Challenger' Brachyura, Eeports, 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 N e w Zealand takes precedence of tbe 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. planatus 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 N e w Zealand and is without teeth to the carapace. In the following notes on specimens brought by Mr. Vallentin from the Falkland Islands, which specimens I take to be with little doubt II. planatus, I propose to compare with them specimens from Jervis Bay in Australia, sent to me by Prof. Haswell, unnamed, but agreeing in m y opinion with H. ovatus Stimpson (Plate X X X V I 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 approximate than in the former. In both species the teeth are setiferous. Of the marginal teeth the hinder, which is much the more pronounced, is more setose in H. planatus; and in this species, as Miers notices, the carapace is much more hairy in some instances than in others, but that variability, for aught we know, may belong to other species of the genus, or even be an incident in the life of the individual. Iu 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 antennae have in both the narrow7 peduncle much shorter than tbe stout one of the first; while Guerin iu 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 external 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 P R O C ZOOL. Soc-1900, No. XXXV. 35 |
