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Show 188 DR. W. T. CALMAN ON THE MACRUROUS [Mar. 6) ii. Systematic Notes and Descriptions of New Genera and Species. Family P A L V E M O N ID./E. P A L ^ M O N MOOREI Caiman. (Plate XI. figs. 1 & 1 a.) P. moorei Caiman, Proc. Zool. Soc. 1899, p. 709, pi. xl. figs. 20-24. The numerous and excellently-preserved specimens of this species which Dr. Cunnington has brought home enable m e to add some further details to the description which I formerly gave. Of 18 specimens collected only two are males. This is a somewhat remarkable fact, since in this genus, as Coutiere remarks, it is rare for the females to be as numerous as the males. The largest specimen is an ovigerous female, 27 m m . in total length. The males are a little smaller. The teeth of the rostrum are 2~3*?~u. The second pair of perseopods in the females (Plate X I . figs. 1 & \a) differ from those of the male formerly figured, and from those of the two males in the present collection, in having two low rounded teeth or tubercles on the inner edge of each of the fingers close to the proximal end. The males do not differ from the females in the length or stoutness of the chelae. The carpus and hand are rough with minute sharp granules or spines, which were not well shown in the figure formerly given. There is some little variation in the relative lengths of the segments of this limb, as the following measurements (in millim.) show:- Merus. Carpus. Palm. Fingers. Female 4-0 4*5 3-6 3-9 „ 4-3 4-9 4-2 3-7 „ 4-7 5-0 3-5 3-9 4-5 4-5 4-5 4-3 Male 2-9 3'3 2-5 3-0 „ 3-6 3-6 2-3 3-1 The mandible carries a palp which, although short (about half the length of the incisor process), is composed of three distinct segments, and in all other respects the species conforms to the definition of the genus * to which I have referred it. As it is by no means easy to determine what are the affinities of this species among the very numerous and closely allied species of the genus, I have submitted a specimen to Dr. J. G. de Man, whose competence to pass judgment on this point will not be disputed. With his accustomed courtesy, Dr. cle M a n sent me a long letter dealing with the subject, and with his permission I quote some of his remarks. After noticing that P. moorei is, without doubt, the smallest species of the genus, and that it has, at first sight, quite the general appearance of some species of * I follow Ortmann, de Man, and the majority of recent authors in retaining the name Paltemon for this genus. I a m unable to understand the reasons which have led some American authors to follow Spence Bate in using for it the name Bithynis. |