622 GEOLOGICAL SURVEY OF THE TEEEITOEIES. 



really of specific value. For this purpose, large numbers of specimens 

 from diflfereut localities at different dates are necessary. After the ob- 

 servations made at Odessa on the wonderful degree of variation in Arte- 

 mia at different seasons of the year and density of the water, we are led 

 to think, from the fact that the females of the above three species of 

 Branchinectes are almost undistinguishable, that the forms are possibly 

 conspecitic, and the differences which have been indicated are the result 

 of climatic and other physical causes. At present, however, it will be, 

 perhaps, wisest to regard them as distinct. 



JEubranchipus, Verrill. — "Body robust; male with large head and very 

 stout claspers ; first joint of clasper much swollen, capable of retracting 

 the basal portion of the second joint into their cavity ; second joint stout 

 at base, in the typical species with a large tooth on the inside, the outer 

 portion tapering, rather obtuse. Front of head between the claspers 

 bears two thin, flat, tapering appendages, serrated on the edges and 

 transversely striated or jointed. Caudal appendages long. Egg-pouch 

 short and thick." — (Verrill.) 



U. vernalis, Verrill. — "Claspers very large and strong; the basal joint 

 much swollen: second joint long, broad, with an angle on the outside, 

 from which it rapidly narrows by strongly concave outlines on each 

 edge, bearing at the constricted portion, not far from the base, a large, 

 strong, very prominent, crooked, bluntly pointed tooth, which is directed 

 inward and backward. Massachusetts and New Haven, Conn. Very 

 early in spring in quiet pools." — (Verrill.) 



Streptocephalus, Baird. — Male-claspers long, three-jointed, tortuous; 

 the terminal joint subdivided more or less into two or more branches, or 

 bearing slender appendages. Male organs long, slender. Egg-pouch 

 elongated or conical. 



iS. Texanus, Pack. (Amer. Jouru. Sc, 1871), (Fig. 13, male enlarged). — 

 Male differs from S. similiSj Baird, from San Domingo, in the longer 

 branch of the inferior antennsB being much longer and slenderer at tip, 

 while the shorter branch is much narrower. Length of male, 0.65 inch; 

 female 0.55 inch. Texas, in pools, in summer, formed by the summer- 

 rnius, which had dried up early in the season; and also in April. — 

 (Belfrage.) 



