1917-] S. Kemp : Notes on Crustacea Decapoda. 247 



As a generic name for this group of species I have emplo3'ed 

 Stimpson's Rhynchoplax,^ though unfortunately I cannot be al- 

 together certain that its application is correct. Stimpson does 

 not state that an}^ parts of the male abdomen are fused and his 

 reference to the external maxillipedes is decidedly confusing, his 

 only remark being " ischium-] oint. . . .scarcely longer than meros," 

 a description that applies if anything better to Halicarcinus than 

 to the group of Indian species. On the other hand Rhynchoplax 

 messor, the type species of the genus from Simoda in Japan, ap- 

 pears specifically to be an exceedingly close relative of Alcock's 

 " Hymenicus^' wood-masoni , both species, apart from other resem- 

 blances, possessing a series of teeth on the upper border of the 

 merus of the chelipede. The question cannot finally be settled 

 until further specimens of Rhynchoplax messor are examined. The 

 types were, I understand, destroyed by fire in 187 1 and the species 

 has not been recorded since Stimpson's time. 



To distribute the numerous described species correctly beween 

 the genera Halicarcinus and Rhynchoplax, as here defined, is a 

 matter of very great difficulty, but from the figures and descriptions 

 which have been published I conclude that the following species 

 may safely be referred to the genus Halicarcinus,^ — Hymenosoma 

 gaudichaudii , Guerin Meneville,^ Halicarcinus pubescens, Dana,* 

 Hymenicus pubescens , Dana,^ Hymenicus varius, Dana," Halicar- 

 cinus ovatus, Stimpson,'' Hymenosoma tridentata, Jacquinot,^ Hy- 

 menosoma rostratum, Haswell,^ Elamene pilosa, A. Milne-Edwards,''^ 

 Hymenosoma laeve, Targioni-Tozzetti," Hymenicus marmoratus, 

 Chilton/* and Hymenosoma lacustris, Chilton. '° 



i Stimpson, Pi'oc. Acad. Sci. Pliiladelpliia, X, p, 109 [55] (1858) and Suiiflis. 

 Misc. Coll., XLIX, p. 147 (1907). 



■^ In addition to the type species of the genus I have seen specimens of 

 H. ovatus, H. vavitis, H. rostratiis and a species from the Australian coast which 

 is perhaps undescribed. 



^ Guerin Meneville, loc. cit. supra p. 245. 



* Dana, U. S. Explov. Exped., Crust., I, p. 386, pi. xxiv, fig. 8. 



^ Dana, ibid., p. 388, pi. xxiv, figs. 11 a-c. 



'^ Dana, ibid., p. 387, pi. xxiv, fig. 9. 



" Stimpson, P7'oc. Acad. Nat. Sci, Philadelphia, X, p. 109 [55] (1858) and 

 Smiths. Misc. Coll., XLIX, p. 146 (1907) ; Stebbing, Proc. Zool. Soc. Lo)idoii, 

 1900, p. 525, pi. xxxviA. Chilton, in Subantarctic Is. Neiv Zealand, p. 609(1910) 

 suggests that //. ovatus is synonymous with Jacquinot's H. tridentata. 



^ Jacquinot, in Hombron and Jacquinot's Voy. an Pule Sud, Zool., Atlas, 

 Crust., pi. V, figs. 27-33, L^sually regarded as a synonym of H. plaiiatus. Chil- 

 ton, loc. cit., 1910, p. 609, suggests its retention at least in a subspecitic significance. 



9 Haswell, Proc. Linn. Soc. N.S. Wales, VI, p. 550 (1882) and Cat. Austral- 

 ian Crust., p. 116 (1882) ; Baker, Trans. Roy. Soc. S. Australia, XXX, p. 114, 

 pi. iii, figs. 2, 2a,b 1 1906). 



'*' A. Milne-Edwards, Nouv. Arch. Mus. Paris, IX, p. J!,22. pi. xviii, figs. 6, 

 6rt-e (1873J. 



^l Targioni Tozzetti, Crost. Viaggio 'Magenta,' p. 179. pi- xi. figs- 3"-'" 



(1877}- 



'•2 Chilton, Trans. N. Zealand Inst., XI\^ p. 172, pi. \ui, figs. \a-c (iSSl). 



'■^ Chilton, Trans. N. Zealand Inst., XIV, p. 172 (1881) [as Elamena'. 

 lacustris']; ibid., XI. IV, p. 128 (1912J ; ibid., XLVII, p. 316, fig. 1 (1915) ; 

 Fulton and Grant, Proc. Roy. Soc. Victoria, XV, p. 59, pi. viii (1902) ; Grant and 

 McCulloch, Proc. Linn. Soc. N. S. Wales. XXXII, p. 153 (1907)- 



