PACKARD.] PHYLLOPODS OF NORTH AMERICA. 345 



the basal joint stout, armed externally at the end with a very long, 

 slender spur, about as long as the joint itself; the 2d joint thick, very 

 long and bent upward and inward; n'earthe end on the inside is a row 

 of small papillse; at the extremity it enlarges into a short, thick hand- 

 like portion, the 3d.joint, which divides into two long unequally forked 

 chitinous appendag-es. 2d anteunse of the female as usual, broad and 

 suddenly mucronate at tip. Eleven pairs of feet; much as in Branclii- 

 necta and Branchipiis : the first endite as usual, but the fringe is rather 

 long, as also that of the other endites; the 5th endite square, the 

 outer edge hollowed out, the spines on the lower edge few and un- 

 usually blunt; the 6th endites more acute than in Branehipus ; the 

 flabellum large and rounded, fuller than in Branehipus ; the gills rather 

 large. The penis consists of two separate very long curved filiform 

 processes. Ovisac of the female long and slender, much as in BrancU- 

 necta. Caudal appendages longer and broader than in BrancMpiis. 



This genus differs from Branehipus in the want of frontal appendages, 

 and may be easily identified by the long 3-jointed twisted and elbowed 

 claspers, and by the two long slender filamental processes forming the 

 male genital armature. Judging by the form of the 2d antennae, par- 

 ticularly the 1st joint, and by the absence of any frontal appendages, 

 and especially the form of the ovisac, Streptocephalus appears to be a 

 modified Branchinecta, and to have been differentiated from that genus 

 rather than from Branehipus; in fact we may, I think, regard Branchi- 

 necta as the more generalized, ancestral type of the family. 



Synopsis of the species. 



Male claspers larger and slenderer at tip than in S. similis .,.S. texanus. 



Male claspers shorter than in S. texanus S. sealii. 



Male claspers shorter and broader at base than in 8. tex- 

 anus .....S. fioridanus. 



Streptocephalus texanus Packard. 



Plate XII, figs. 1-7. 



Streptocephalus texanus Pack., Amer. Jonrn. Sc. August, 1871. 



Streptocephalus ivatsomi Packard, Havden's Annual Report of the IT. S. Geol. & Geogr. 

 Survey of the Territories for la73, p. 622. PL IV, fig. 13. 



Male. — "Front of the head with a small median lobe which projects 

 downward between the bases of the second antennse, and is flattened, 



Tig. 20. Streptocephalus texanus, enlarged. 



broad at the end, but not lobed, there being but a very faint median 

 sinus. The subcorneal upper surface of the head bearing the oblong 

 ocellus near the front edge is truncated- conical, being a little longer than 

 broad. 1st antennae long and slender, twice as long as the eyestalk, 



