1SOPODS OF NORTH AMERICA. 553 



The outer branch of each pleopod is elongate and simulates the uro- 

 poda in appearance. The outer branches are all similar in shape and 

 of nearly equal size. The inner branches are small, elongated or 

 rounded, and sac-like. They are not conspicuous in a dorsal view, 

 whereas the outer lamellae form a conspicuous border around the 

 abdomen, where they seem to be attached to the lateral margins of 

 the segments. 



There are five pairs of incubatoiy lamellae which entirely inclose 

 the marsupial cavity, the lamellae overlapping in the medial ventral 

 line. The basis of all the legs is furnished with a high rounded carina. 



The male is 4r mm. long and 1 mm. wide in the region of the 

 thorax. The abdomen at the base is 2 mm. wide. The anterior mar- 

 gin of the head is rounded. The eyes are absent. The first pair of 

 antennae are composed of three articles. The second pair are composed 

 of five or six articles. All seven segments of the thorax are distinct. 

 The legs are all prehensile. 



The segments of the abdomen are consolidated in a single segment, 

 which is wider at the base than the segments of the thorax. Its pos- 

 terior margin is widely rounded. Near the base of the segment is a 

 single prominent tubercle in the median line. There are no pleopoda 

 nor uropoda. 



94. Genus PROBOPYRUS Giard and Bonnier. 



Segments of abdomen in female dorsally defined; lateral parts or 

 pleural lamellae not developed. 



Five pairs of double-branched pleopods are present. 



Uropoda wanting. 



Segments of abdomen in male fused dorsally, but defined on the 

 lateral margins. Five pairs of small tuberculiform pleopods present. 

 Uropoda wanting. 



Branchial parasites. 



ANALYTICAL KEY TO THE SPECIES OF THE GENUS PROBOPYRUS. 



a. Male with the first four segments of the abdomen defined laterally by deep 

 incisions, the last two fused in a large and broad terminal piece. 



Probopyrus pandalicola (Packard) 



a' '. Male with all the segments of the abdomen defined laterally by deep incisions. 

 b. Species large. First incubatory lamella with the distal segment produced poste- 

 riorly in a lobe at the outer angle. 



c. Abdomen of male nearly as long as broad. . .Probopyrus floridensis Richardson 

 c / . Abdomen of male nearly twice as broad as long. 

 d. Body of male wide, thick-set; head and thorax two and a half times or less 



longer than abdomen Probopyrus bithi/nis Richardson 



d'. Body of male narrow; head and thorax three and a half times longer than 



abdomen Probopyrus ulphei Richardson 



&'. Species small. First incubatory lamella with the distal segment produced 

 posteriorly at the inner angle Probopyrus latreuticola ( Gissler) 



