560 PROCEEDINGS OF THE NATIONAL ISIUSEUM vol.84 



figure 1 is a ventral view of the genital segments of the specimen in 

 ■which the penes were farthest protruded. The penes in this indi- 

 vidual are about 2.2 mm in length. On the inner side, near the 

 proximal end, is a conical spur, 410 /x in length, and on the lateral 

 side, near the distal end, is a rounded eminence, 360 ju, in diameter, 

 covered with short conical spines 20 fi in height. At the tip of the 

 everted penis, on its lateral side, is a second eminence, about 200 fi in 

 diameter, of similar appearance and spination. 



The testes extend from some j^art of the third, or the anterior 

 region of the fourth, abdominal segment anteriorly into the first 

 genital segment. Near the junction of the two genital segments a 

 vas deferens leaves each testis and courses ventrally and posteriorly 

 to communicate with the penis. A large ventral outpocketing of the 

 vas deferens near its junction with the penis serves as a seminal 

 vesicle. 



The ovaries originate in some part of the fourth or fifth abdominal 

 segment and extend anteriorly into the seventh (rarely only into the 

 eighth) thoracic segment. They are crowded with eggs of irregular 

 or angular shape from mutual pressure. Near the boundary be- 

 tween the two genital segments a conspicuous oviduct passes from 

 each ovary into the ovisac. The ovisac has an elongated piriform 

 shape, thus differing from that of most species of the genus in which 

 it is more or less fusiform. There are paired cement glands over- 

 lying the dorsal side of the egg mass for about three-fourths the 

 length of the ovisac and extending laterally and ventrally to the egg 

 mass in the proximal one fourth of the ovisac. By actual count the 

 number of eggs present in the ovisacs of three specimens was 210,, 

 256, and 595, respectively. Apparently mature eggs from preserved 

 specimens are 580/x (570/u.-595/a) in diameter. 



There are seven abdominal (postgeniLal) segments. The terminal 

 one is bifurcated and bears the anus, Avhich is a vertical slit at the 

 junction of the two short limbs of the bifurcation. Each cercopod 

 is attached to the ends of the seventh segment by an obscure articu- 

 lation. The cercopods curve outward, often with a slightly spiral 

 twist (pi. 80, fig. 3). 



Bema?'ks. — Branchinecta gigas^ by far the largest known species 

 of the genus, is the fourteenth species of Branchhiecta to be described 

 and the fifth reported from North America. Only B. ferox (Milne 

 Edwards) from eastern Europe and Asia Minor, in which the males 

 reach a maximum length of 51 nnn, the females of 70 mm, ap- 

 proaches this new species in size. B. gigas differs from all known 

 species of the genus in its large size and in having the antennae of 

 the female as long as those of the male. It is the only species known 

 that is wholly without tubercles, processes, or denticulations on the 



