NO. 6 DECAPOD AND OTHER CRUSTACEA — SCHMITT 23 



KEY TO THE SPECIES OF THE GENUS PERCNON 



A 1 . Pilose groove along upper margin of chelae about or nearly as long as the 



upper margin of palm. 



B 1 . Anterior margin of epistome armed with three spines, one median and one 



at either end. 



C 1 . Second of lateral teeth of carapace, counting the one at anterolateral 



angle, inconspicuous, very much smaller than third or indeed any 



of the others (this character holds for even the smaller specimens). 



Carapace squarish, scarcely if at all longer from notch in extremity 



of rostrum to posterior margin than wide ; rostral notch shallow, the 



spines forming it widely spread dbbreviatum (Dana). 



(Proc. Acad. Nat. Sci. Philadelphia, vol. 5, p. 252, 1851 ; Crustacea 



U. S. Explor. Exped., vol. 1, p. t>73, 1852, atlas, pi. 23, fig. 11, 1855.) 



C". Second lateral tooth at most only slightly smaller or shorter measured 



on the outer margin than third. Carapace longer from rostral notch 



to posterior margin than wide ; rostral notch not noticeably shallow 



nor spines forming it particularly widespread 



p'dimamis (A. Milne-Edwards). 6 

 (Nouv. Arch. Mus. Hist. Nat. Paris, vol. 9, p. 300, pi. 14, fig. 5, 

 I873-) 

 B 2 Anterior margin of epistome with but a single, the median, spine. Second 

 of lateral teeth of the carapace, counting the one at the anterolateral 

 angle, of good size, but smaller than third, measured on the outer mar- 

 gin only about two-thirds as long as the third. Carapace more or less 



rounded or narrowed anteriorly, longer than wide demani Ward. 6 



(Bull. Raffles Mus., No. 9, p. 24, pi. 3, fig. 3, 3a, 1934.) 

 A 3 . Pilose groove on upper margin of chela relatively short, never more than 

 half the length of the palm, often much less. Pubescence on palm other 



5 This species, at least in well-developed males, is characteristically distin- 

 guished from all other Percnons by the conspicuous, thick, felted patch of hair 

 on the inner side of the palm, and on the inner upper surface of the merus. In 

 some females that I have seen, the pilose patch is not only reduced in size, but 

 the hairs forming it are shorter and less conspicuous than in the male. I have 

 examined three specimens lent me by the Museum of Comparative Zoology 

 through the kindness of Dr. Fenner A. Chace, Jr., in which the second lateral 

 tooth is a little smaller and shorter than the third, if only slightly so. In Milne- 

 Edwards' figured type the reverse seems true ; the second tooth, as drawn, is 

 definitely larger and stouter than the third. 



8 In the U. S. National Museum collections I have discovered four specimens, 

 two small females from the Philippines and a small male and medium-sized 

 female from the Celebes, which I believe represent the species which de Man 

 had questionably assigned to P. abbrcviatum (Dana) and on which Ward quite 

 rightly bestowed a new name, demani. De Man was influenced in his tentative 

 determination by the reduced size of the second lateral tooth of the carapace, 

 which, however as he remarked, can in no sense be described as inconspicuous. 

 It is very inconspicuous in true abbrcviatum. In Ward's halftone illustration of 

 demani the second lateral tooth appears at least as large or as long as the third, 

 if not longer. Unless this second tooth is noticeably smaller than the third in 

 the specimen itself, the figure represents a species other than demani. 



