308 Henry Woodward — Fossil Crab from Mehran Coast. 



Portunus, Scylla, and Neptunus are specially modified to serve as 

 natatory appendages, their joints being flattened and expanded for 

 swimming, and are carried above the carapace when not used in 

 natation, the three other pairs of simple feet serving as walking and 

 running appendages. Only a fragmentary remnant of one of these 

 swimming feet is preserved on the left side behind the large costal 

 spine. 



De Haan, in Siebold's "Fauna Japonica," * distinguishes three 

 equivalent subgenera, Neptunus, Amphitrite, and Pontus. They are 

 all characterized by the large size of the costal spine. The sub- 

 divisions are based upon the form of the third endopodite joint of 

 the outer maxillary feet. In Neptunus this joint is longer than 

 broad, with the lower inner angle conspicuously produced, and with 

 the upper hinder edge rounded. In Amphitrite the upper hinder 

 edge of the third endopodite is considerably produced and also 

 rounded. In Pontus the same joint is said to be square. 



Amphitrite was accepted by Dana,^ but united with Neptunus by 

 Alphonse Milne-Edwards.^ But the character relating to the form 

 of the third joint seems to be subordinate. 



Stoliczka had already observed (Crust, from Kutch and Sind, 

 op. cit., p. 3) that " it is remarkable to find the Amphitrite form 

 already represented in fossil species from Kutch " (as noticeable in 

 his N. Wynneanns) ; he adds, however, that the name Amphitrite had 

 been already used by Miiller in 1771 as a generic name, and there- 

 fore it cannot be reinstated, but must remain a synonj'm of Neptunus. 



As all the species already recorded in a fossil state have been 

 obtained from beds older than the formation at Ormara yielding the 

 fossiliferous concretions,* I have compared our crab with De Haan's 

 figures and descriptions of recent (living) species from the Indian 

 Ocean and the Sea of Japan. The first of these figured by him 

 is Neptunus pelagicus, probably the largest and most powerful 

 swimming-crab living, with a carapace twice as wide as it is deep, 

 with long and powerful costal spines, a regularly arched front armed 

 with eight equal serrations on each side ; the powerful chelate 

 fore-arms are considerably longer than the extreme breadth of the 

 carapace. It is, however, in De Haan's subgenus "Amphitrite" that 

 species are found which most closely resemble our fossil form. 



In Neptunus (Amphitrite) hastatoides, Fabr. (De Haan, tab. i, 

 fig. 4), the costal spines are equal to half the breadth of the 

 carapace ; two short spines are also present, one at each postero- 

 lateral angle of the carapace behind the insertion of the fifth pair of 

 swimming feet. 



• Crustacea, by W. de Haan, 1850, Leyden, 4to, with 70 plates. 



2 J. D. Daua: " Classification and Distribution of Crustacea," 4to, 1853, p. 1424. 

 Fam. IV, Portunidae. 1, Lupinae. Genera: Scylla, De Haan; Lnpa, Lh. ; 

 Amphitrite, De Haan; etc. 



3 A. Milne-Edwards, Hist. Crust. Podoph. Foss., 1861-5, tome i, p. 100, gives 

 genus Neptunus (synonymy : Cancer, pars, Linne ; Fortmiiis, Fabr. ; Lnpa, pars, 

 Leaeh ; etc.). NeptuiiHs, Pontus. ei Amphitrite, pars, De Haau ; Lupa ei Amphi- 

 trite, pars, Dana : Expl. Exped. Crust. 



* See Mr. Newton's remarks ante, pp. 29C and 300. 



