1882.] CRUSTACEANS FROM MAURITIUS, 341 



rostral spines shorter, the chelipedes rather slenderer, and the first 

 pair of ambulatory legs somewhat less elongated. 



Tlie nearest ally to this species with which I am acquainted is 

 Naxia (Naxioides) petersii {Poclopisa petersii, Hilgendorf, Monatsb. 

 Ak. Berhu, p. 785, pi. i. fig. 5, )878), from Mozambique, which is 

 very probably identical with Naxioides hirta, Alph. M.-Edwards 

 (Ann. Soc. Entom. France, ser. 4, v. p. 143, pi. iv. fig. 1, 1865), 

 from Zanzibar. N. robillardi is at once distinguished by its 

 greater size, by having the carapace covered with strong conical spines 

 in the place of small irregular tubercles, and by the double hiatus 

 in the upper orbital margin. In the last-mentioned character it 

 resembles certain species of Pisa (e.g. Pisa {Arctopsis) latiata) ; but 

 it is distinguished from that genus by the greater length and slender- 

 ness of the chelipedes and first ambulatory legs, by the narrower 

 basal antennal joint, and the accessor}^ spines of the rostrum ; yet it 

 may be regarded as establishing a transition to Pisa. 



In my revision of the Maioidea ' I adverted to the insufficiency 

 of the characters assigned to Naxioides, A. M.-Edw. (Podopisa, 

 Hilgendorf) for distinguishing this genus from Naxia. As the species 

 now described has a distinct prseocular spine, even this character can 

 no longer be cited as peculiar to the last-named genus. 



Callianassa mauritiana, sp. n. 



Both the specimens sent by M. Robillard are imperfect ; and the 

 large chelipede, from which the principal distinctive characters are 

 derived, does not appear to belong to either example, but to a 

 distinct and larger individual. In the analytical table appended to 

 M. A. Milne-Edwards's monographic revision of the genus Callia- 

 nassa", our new species will be arranged with Callianassa subterranea 

 and C. longimana, inasmuch as there exists a small median rostral 

 tooth, the terminal segment of the postabdomen and the eyes are 

 well developed, and there is a tooth or lobe, which is itself den- 

 ticulated, at the proximal end of the inferior margin of the merus 

 joint of the larger chelipede, vihose penultimate joint or palm about 

 equals the wrist in width. It is distinguished from both the above- 

 mentioned species, however, by the broad spinulose inferior basal 

 lobe of the arm or merus, and by having the distal end of the palm 

 between the bases of the fingers deeply excavated as in G. califor- 

 niensis and C. uncinata ; the inferior margin of the merus is armed 

 with small granulations ; the carpus (in the large chelipede) is some- 

 what shorter than the palm, with its upper margin acute ; the palm, 

 which is not once and a half as long as broad, narrows very 

 slightly toward the distal end, its upper margin is rounded, except 

 at its pro^imal end ; the lower margin, both of wrist and palm, is 

 minutely serrated ; the upper or mobile finger is longer than the 

 lower, and is sharply uncinated at its distal end, it has a strong 

 blunt tooth on its inner margin near the base. I may add that the 



' Jouru. Linn. Sue. Zuol. siv. p. 658 (1879). 



' NouTelles Archives dii Museum, vi. p. 101 (1870). 



