I9I9-] S. Kemp : Notes on Crustacea Decapoda. 389 



Macrophthalmus convexus, Stimpson. 

 (Plate xxiv, fig. 2.) 



igoo. MacrophiJinlmus co)ivexus Alcock, Jonvn. Asiat. Soc. Bengal, LXIX, 



P- 378. 

 1915, MacropJithalmits convexiis, Tesch, Zool. Meded. Mus. Leideu, 1, 

 p. 175, pi. viii, fig-. 8. 



A large male from the upper end of the Gulf of Manaar is 

 referred with considerable doubt to this species, for it differs widely 

 from all other adult specimens of the same sex that I have seen in 

 the form of the chelae (fig. 2). 



In normal males from Indian waters the chela agrees exactly 

 with the figure of M.inermis published by A. Milne-Edwards in 

 1873 ', M. inermis being regarded b}' most authorities as a syno- 

 nym of M . convexus. In the abnormal male from the Gulf of 

 Manaar the form is altogether different, resembling that of females 

 and very young males. 



The chela in this specimen is about 2| times as long as the 

 height at the base of the fingers and the dorsal edge of the palm 

 bears a double row of small tubercles not seen in normal males. The 

 outer surface is minutely granulate in its upper part ; but lower 

 down, above the strong serrate carina that runs from the base to 

 the tip of the fixed finger, it is concave and perfectly smooth. 

 In normal males the fingers and a small portion of the palm in 

 the vicinity of the finger-cleft are clothed with hair internally, but 

 in this specimen the hairy covering extends over practically the 

 whole of the inner surface. The prehensile edges bear only rudi- 

 ments of the large teeth found in normal males and the fixed 

 finger is scarcely at all deflexed. The chela differs from that of 

 the female in only two points, — in the possession of rudimentary- 

 teeth on the fingers and in the hairy covering of the inner surface. 



In all other respects the specimen agrees precisely with nor- 

 mal examples of the species. It is, however, unusually large, the 

 breadth of the carapace being 32*5 mm. and the length i6*5 mm. 

 An ovigerous female found with this male is 23* i mm. in breadth 

 and I2"2 mm. in length ; it is as nearly as possible identical with 

 other females taken in company with normal males. 



It is difficult to come to any satisfactory conclusion regarding 

 the identity of these two specimens ; I believe, however, that they 

 are to be referred to M. convexus (=M. inermis). The abnormal 

 character of the chelae of the male is perhaps to be explained by 

 regeneration ; but, if so, the original chelipeds must both have 

 been lost at the same time and at a very early age. 



Tesch has followed de Man and Alcock in regarding M. 

 inermis as a synon^-m of M . convexus. Miss Rathbun considers 

 them distinct and has noted various points of difference, but I am 

 not at all certain that the statements are derived from actual 

 comparison of specimens. It appears probable that the informa- 



' A. Milne- Edwards, Nouv. Arcli. Mus. Hist. Nat. Paris, IX, p. 277, pi. xii, 

 fig- 5 (1873)- 



