NO. 6 
DECAl’OD AND OTHER CRUSTACEA SCHMITT 
23 
KEY TO THE SPECIES OF THE GENUS PERCNON 
A^. Pilose groove along upper margin of chelae about or nearly as long as the 
upper margin of palm. 
Anterior margin of epistome armed with three spines, one median and one 
at either end. 
O. 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 abbrcz lafiuii (Dana)’. 
(Proc. Acad. Nat. Sci. Philadelphia, vol. 5, p. 252, 1851 ; Crustacea 
U. S. Explor. Exped., vol. i, p. 373< 1852, atlas, pi. 23, fig. ii, 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 
pUhnaniis (A. Milne-Edwards) 
(Nouv. Arch. Mus. Hist. Nat. Paris, vol. 9, p. 300, pi. 14, fig. 5 , 
1873-) 
B“ 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 . . . .dcnianl Ward.® 
(Bull. Raffles Mus., No. 9, p. 24, pi. 3, fig. 3, 3a, I934-) 
A“. 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 
“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. Eenner 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. 
®In the U. S. National Aluseum 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. abbi^cviatuiii (Dana) and on which Ward quite 
rightly bestowed a new name, dcinaiii. 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 abbrezbatiiiu. In Ward s halftone illustration of 
dcmani 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 dcruanu 
