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Show 710 MR. W. T. CALMAN ON MACRl'ROUS [May 16, is equal in length to the merus, somewhat expanded distally, where the breadth is about one-fifth of the length. The hand is rather wider than the distal end of the carpus, not perceptibly compressed (the two diameters are about as 5 : 6), a little less than twice the length of the carpus Palm shorter than the carpus, and rather shorter than the fingers. Fingers straight, meeting along their whole length ; inner margins with smooth cutting-edges, without any trace of teeth save a single verv minute tubercle near the base of the dactylus. The surface of the whole limb bears widely-scattered very minute setae ; on the distal part of the carpus and on the inner side of the palm are a number of small spinules. The succeeding pairs of peraeopods are long and slender, the fourth pair extending beyond the antennal scale. The dactylus is nearly one-third the length of the propodus. End of telson (Pl. X L . fig. 24) with a sharp median point, longer than the outer but shorter than the inner pair of terminal spines. Seven specimens, most of them very imperfect, are in tbe collection ; only one of the large chelae is preserved. One specimen is a female carrying ova. The species was dredged at a depth of 50 feet. Length of largest specimen (6), 25 m m. Length of ovigerous female, 23 m m. Length of specimen figured (<$ ), 18 m m. Length of 2nd peraeopod of same, 11*5 m m. The very large number of closely-allied species included in the genus Palcemon, and the very great differences (as yet only partly elucidated) which may exist between individuals of the same species of different ages and sexes, render it somewhat hazardous to attempt to define a new species from such scanty material. The presence of an ovigerous female in the collection shows that the species is one of the smallest, if not the very smallest species of the genus. On the other hand, we cannot be quite certain that the single male specimen upon which our description is mainly based has attained its full development in the characters of the chela1. Assuming, however, for the present that this is the case, the species will fall into the group Eupalcemon as defined by Ortmann (Zool. Jahrb., Abth. f. Syst. v. 1891, p. 696), in which the second peraeopods are cylindrical, w hile the equality of the merus and carpus of these appendages and the characters of the telson will bring it into proximity with such species as P. scabriculus Heller and P. en d< hen sis de Man. P. niloticus Boux, the only species known from North Africa, is somewhat similar to the present form, but, so far as can be indeed from the more or less defective figures and descriptions of Boux (Ann. Sc. Nat. xxviii. 1833, p. 73, 1 Since this paper was read I have received several additional and better preserved specimens of both sexes from Mr. Moore's collections. They agree in all essential points with the description given above. |