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PROCEEDINGS OF THE NATIONAL MUSEUM. 



vol. 42. 



which extend the length of the ovarian bosses. On the last three 

 segments the epimera occupy the entire lateral margin. 



All six segments of the abdomen are distinct. The sixth or ter- 

 minal segment has a small rounded notch in the middle of the pos- 

 terior extremity. There are five pairs of double-branched pleopoda, 

 a pair for each of the first five segments. The uropoda are absent. 

 There are five pairs of incubatory plates; the first pair has the ter- 

 minal extremity of the distal segment produced in a short, broad, 

 rounded lobe. (See fig. 7.) All the incubatory lamellae are marked 

 with reddish-brown, those on one side being more completely cov- 

 ered than those on the other side. The legs are all prehensile, with 

 a high carina on the basis. (See fig. 8.) 



The male is rather short and thickset, being twice as long as wide. 

 The head is small, with the anterior margin widely rounded; its pos- 

 terior margin is produced backward in a peculiar way, being deeply set 

 in the first thoracic segment. (See fig. 6.) Eyes are present, situated 

 in the post-lateral angles. All the segments of the thorax are dis- 

 tinct. The first four segments of the abdomen are distinct at the 

 sides, but more or less confluent in the middle of the dorsal surface; 

 the last two segments are fused in a single terminal piece, the in- 

 cisions at the sides indicating the two segments. There are three 

 pairs of rudimentary pleopoda, but no uropoda. 



Two specimens of this species were collected by Doctor Meek and 

 Mr. Hildebrand in a small creek at Pariso, Canal Zone. They were 

 parasitic on Macrobranchium acanthurus (Wiegmann), being found 

 in the branchial cavity. 



The type is Cat. No. 43503, U.S.N.M. 



This species differs from all the described species of the genus from 

 the Atlantic Coast of North America in the presence of a notch in 

 the terminal abdominal segment of the female. Probopyrus jior- 

 idensis, however, has a minute excavation. The first incubatory 

 plate of the female is different in the two species, as well as the color 

 markings; the head, abdomen, and proportions of the male are also 

 different. The shape of the head and of the abdomen of the male 

 is different from any of the described species. 



