8 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 122 



Remarks. — The largest specimen has four spines on the anterior 

 borders of the arms of the chelipeds; all of the remaining chelipeds 

 bear three spines on these borders. All specimens have the charac- 

 teristically swollen branchial regions of the carapace. 



This species, which is close to C. miles, has the undersurface of the 

 immovable finger smooth and rounded, whereas in C. miles it is 

 deeply grooved. There are also differences in the last anterolateral 

 teeth, which are longer and more laterally directed in C. riversandersoni. 



The tw^o species were also distmguishable by the pigmentation of 

 the present recently preserved specimens. In C. riversandersoni the 

 red pigment on the under side of the immovable finger of the cheliped 

 did not extend along its entire length, while in C. miles it extended to 

 the distal part of the palm. In the larger males of C. riversandersoni 

 there was a pale circle in each postlateral area of the carapace, bor- 

 dered by deeper pink. This had no counterpart in C. miles. 



Sakai's (1939) colored plates of fresh material of the two species 

 clearly show the differences in the last anterolateral teeth and in the 

 pigmentation under the immovable finger, but they show^ C. riversan- 

 dersoni with three pale areas in the postlateral portion of the carapace 

 (pi. 46: fig. 1) and C. miles \\dth one pale area (pi. 46: fig. 2). Sakai's 

 (1965) plates again show the differences in last anterolateral teeth, 

 show even more clearly the differences between the colors of the 

 immovable fingers, but show one indistinct light postlateral patch in 

 C. riversandersoni (pi. 60: fig. 2), agamst a very distinct patch in 

 C. miles (pi. 61). 



Distribution. — Previously Konkak Coast, Bay of Sagami, South 

 China Sea, and now Arabian Sea and Gulf of Oman. 



Charybdis rostrata (A. Milne EdMards) 



Goniosoma rostratum A. Milne Edwards, 1861, p. 379, pi. 35 (figs. 2, 2b).— Hen- 

 derson, 1893, p. 377. 



Charybdis {Goniosoma) rostrata (A. Milne Edwards).— Alcock, 1899a, p. 59.— 

 de Man, 1925, p. 326, fig. 2.— Chopra, 1935, p. 491, fig. 12. 



Charybdis (Charybdis) rostrata (A. Milne Edwards).— Leene, 1938, pp. 78-81, 

 figs. 39, 40. 



Material examined. — 1 female (24 mm), Sta. No. AB-37. 12 

 males (17-25.5 mm), 50 females (16.5-25 mm), 1 ovig. female (21 mm) 

 (many specimens cephalothorax only), Sta. No. AB-40. 18 males 

 (12-27 mm), 12 females (16.5-25.5 mm), 1 Sacculin a-infested specmien 

 (22.5 mm), Sta. No. AB 44-63. 1 male (16.5 mm), 6 females (18.5- 

 22.5 mm), Sta. No. AB 44a-63. 1 male (21.5 mm), 1 yg. (5 mm), 

 Sta. No. AB 45-63. 



All trawled, depths from 15 to 81 m. 



