PACKARD.] PHYLLOPODS OF NORTH AMERICA. 351 
Genus CHIROCEPHALUS Prevost. 
Plate XIII. 
Chirocephalus Prevost, Journal de Physique, lvii, 37, 1803; Thompson, Zoological Re- 
searches, 1834. 
Branchipus, Milne-Edwards, Fischer, Latreille, Desmarest, Guerin, Lamarck. 
Chirocephalus Baird (in part), British Entomostraca, 38, 1850; Annals and Mag. Nat. 
Hist. 2d ser. xiv, 221, 1854; Verrill, Proc. Amer. Assoc. Adv. Se., July, 1870. 
Body slender, head of moderate size, 2d antenne or male claspers 
with the basal joint very large and thick and somewhat curved; 2d 
joint very long and slender, curved inward, with a basal sharp spur. 
Two remarkably long and large frontal appendages arising between 
the base of the 2d antennx, about twice as long as the 2d antenne, 
much twisted and coiled and variously lobed and spinulated. Eleven 
pairs of swimming feet; the basal lobe or endite long and with the edge 
regularly curved, the 2d with an outer subdivision about 4 as broad 
as the Ist; each paler, with rather long fringe of delicate hair-like sete ; 
the 2-4th endites, as in the foregoing genera, small, each with three 
or four long minutely spinulated sete. The 5th endite of the usual 
size, but rather square, much as in Branchipus, but with a tendency in 
the lower outer angle to be somewhat produced so as to be subtriangu- 
lar in outline. (PI. XII, fig. 1.) The 6th endite is unusually long and 
narrow, almost lanceolate, and with long sete in the 3d pair of feet, or 
small, narrow, and abruptly rounded in the Ist pair; in the 10th pair 
they are narrow and rounded at tip. Flabellum and gills much as in 
Branchipus. 
Male genital apparatus short and small, deeply cleft, forming two 
slender curved portions, each with its cirrus. Caudal appendages long 
and broad, much more so than in Branchipus. 
In the female the 2d antenne have the mucronate spur or tip larger 
and longer than usual. Ovisac short and broad, with the end produced 
like the neck of a bottle, much as in Branchipus. The eggs are few in 
number (about a dozen), and the eggs are larger than in Streptocephalus 
and Branchipus. 
This genus differs from Branchipus in the slenderer body, the very 
long, coiled, twisted, lobulated, and spinulose frontal appendages, and 
in the differences in the endites already noted. In the form ot the ex- 
ternal male organs and of the ovisac the genus approximates closely to 
Lranchipus, and in the frontal appendages, as seen in the European C. 
diaphanus, is only an exaggeration of those of Branchipus. It seems 
reasonable to infer that Chirocephalus isa more recent group than Bran- 
chipus, and has probably originated from that genus, as Sireptocephalus 
has in all probability arisen from individuals. The singular frontal ap- 
pendages are supplied with two large muscles, and as no nerves have 
as yet been detected in them it is probable that the organs are simply 
prehensile and perhaps of use during the union of the sexes. 
CHIROCEPHALUS HOLMANI Ryder. 
Plate XIII, figs. 1-5. 
Chirocephalus holmani Ryder, Proc. Acad. Nat. Sc., Philadelphia, 148, 1879. 
Body rather slender; 2d antenne or claspers of the male with. the 
the 2d joint considerably shorter than the 1st; it is forked, spur 
large and pointed; the longer branch slender (its tip crossing that of 
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