108 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 113 
Head as wide as the first segment; median furrow of the vertex 
narrow but strongly impressed; antennae separated by a distance 
equal to the diameter of a socket; joints 2 and 5 subequal in length 
with joint 6 slightly shorter. 
Segment 1 subreniform, the sides rounded witha raised rim, posterior 
margin slightly emarginate at middle. Segments 1 to 4 subequal in 
width, noticeably narrower than those that follow. Segment 2 pro- 
duced forward into an acute angle on each side below the lateral 
margin of segment 1; surface behind it with a thin longitudinal ridge 
extending to the posterior margin. Segments 3 and 4 with each lateral 
carina reduced to a slight swelling set off above, but not below, by a 
fine sulcus; ensuing poriferous carinae represented merely by a swollen 
prominence, broad in front and converging to a low angulation near 
the posterior margin, the swelling set off above by a strong sulcus and 
by a weaker one below; pore located a short distance in front of the 
angulation on usual segments; on poreless segments the swellings are 
much less prominent; segment 17 with pore swelling reduced and 
absent from segments 18 and 19. 
Metazonites of segments 5 to 18 with a strongly impressed transverse 
median sulcus not reaching the pore swellings: other segments without 
trace of asulcus. Segments 4 to 16 or 17 with a thin but pronounced 
crescentic ridge, bowed downward, on each sidea third of the way from 
the base of the legs to the carinal swelling. Last segment with apex 
much exceeding the valves and decurved. Preanal scale triangular, 
two-thirds as long as wide. 
Gonopod as shown in figure 60. 
Male with joint 3 of legs 4 to 7 with a small conic, setiferous tubercle 
at the apical fourth on the lower side; a dense cushion of hairs on 
ventral face of two outer joints of all legs except the last two pairs. 
Genus Orthomorpha Bollman 
Orthomorpha Bollman, U.S. Nat. Mus. Bull. 46, p. 159, 1893. 
Orthomorpha coarctata (Saussure) 
Polydesmus coarctatus Saussure, Mém. Soc. Phys. Nat. Genéve, vol. 15, p. 297, 
pl. 3, fig. 18, 1860. (For additional synonymy, see Chamberlin and Hoffman, 
U.S. Nat. Mus. Bull. 212, p. 83, 1958.) 
Several specimens, Barro Colorado Island, Canal Zone, January and 
February 1955, C. W. Rettenmeyer. 
