172 GEOLOGY AND PALEONTOLOGY OF THE WEST INDIES. 



Relationships. This species differs, it will be seen, from typical 

 Scylla by having the hands costate. One sees in Scylla serrata 1 the 

 vestige of a costa in the same place where the middle costa ends distally 

 in S. costata. In other respects this is a true Scylla, as shown by the 

 smooth carapace with 9 lateral teeth, the posterior of which is not 

 elongate, and by the massive chelipeds. The large distal protuber- 

 ances on the outer and inner surfaces of the hand are similar to those 



of serrata. 



Genus PORTUNUS Weber, 1795. 



Portunus gabbi, new species. 

 (Plate 3, Figures 2 to 7; Plate 6, Figures 1 and 2.) 



Type locality. Lower half of the valley of the Yaqui del Norte 

 River, in the northern part of Santo Domingo, Haiti; probably lower 

 Miocene; W. M. Gabb, collector. 



Holotype. Female. Cat. No. 2256, Mus. Phila. Acad. Nat. Sci. 



Measurements. Length of carapace, median, 45 mm., width of 

 carapace in front of lateral spines 76 mm., width between outer angles 

 of orbits 43 mm., length of manus above, 26.3 mm., distal height of 

 manus 22.2 mm. 



The following is a description of this species : 



The carapace of the holotype is broken in the middle, whence a crack extends 

 to the left margin between the fourth and fifth teeth; the large lateral spines are 

 both broken off at their base. Carapace very convex; the two areoles at the 

 inner angle of the branchial region are strongly marked. The granules, which 

 are large and numerous on the more elevated portions, are scanty toward the 

 second to fifth lateral teeth, inclusive, and along the postero-lateral margins, 

 and are very small and flat behind the front and on the intestinal region. The 

 anterior of the gastric ridges can be made out and is very irregular, the 

 posterior ridge is obscured by the break. The four frontal teeth are sub- 

 triangular, blunt, those of the middle pair wider than those of the outer pair, 

 and definitely more advanced; median sinus V-shaped, lateral sinuses U-shaped. 

 The lateral teeth of the carapace (to be seen best on the left side) appear 

 conical in dorsal view, their sides being straight; tips all broken off. Base of 

 lateral spine granulate and lacking an axial line of granules. 



The right chela is the only one remaining; its manus has the four customary 

 longitudinal ridges on the outer surface, but these are so broken away that 

 one can not tell if they are granulate; the distal extremity of the second ridge 

 (counting from the top) is smooth and punctate. The development of the 

 double lobe at the outer articulation with the dactylus indicates that this is 

 the larger of the two chelipeds. The fingers are covered with such a fine 

 granulation as to be smooth to the naked eye, and have a triangular gape 

 between them; the molariform teeth are unequal and dark-colored; the end 

 of the fixed finger has the same dark color; the terminal fourth of the dactylus 

 is missing. 



The female abdomen is very broad, as in adult Portunus; there is a blunt trans- 

 verse ridge on the middle half of the fourth and fifth segments; outlines not 

 well shown,, but the sides of the sixth segment converge gradually. 



1 See Alcock, Jour. Asiat. Soc. Bengal, vol. 68, p. 27, 1899. 



