458 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.40. 



gular process in the middle fitting closely against the strongly com- 

 pressed, square-cornered, thin-edged, basal joints of the legs. 



The last segment of Docodesmus is larger than in Iomus and with 

 two large tubercles on its upper surface, as well as having the pos- 

 terior border trilobate, but in Iomus the tubercles end with segment 

 19, the last segment having no exposed surface for the accommodation 

 of such tubercles, only the lobed margin being exserted beyond the 

 rim of segment 19. In Tridesmus also the last segment is distinctly 

 exposed behind the posterior edge of the penultimate segment. 



IOMUS INCISUS, new species. 



Type-specimen. — Cat. No. 806 U.S.N.M., collected near Mayaguez, 

 Porto Rico, November 30, 1899, by O. F. Cook. 



Length of male 10.5 mm., width 2.8 mm.; female 12.5 mm. by 

 3.4 mm. 



Color of dorsal surfaces black, also the vertex of the head, the 



under surfaces of the first segment and carinas and the sides of the 



segments below the carinas. Sterna, legs, antennas, lower half of 



head, anal valves and preanal scale, whitish 



or hyaline. 



Head strongly depressed, much exceeded by 

 the projecting margins of the first segment. 

 Vertex rather strongly convex, sulcus rather 



""■iSSSSZlSr dee P> surface str ° n g'y granular-hispid like the 



surfaces of the segments. Clypeus smooth and 

 nearly flat, with three rather sharp teeth in a shallow emargination 

 subtended by ten or twelve widely separated setae arranged in two 

 rows. 



First segment distinctly narrower than the second, but over three 

 times as long in the middle line; anterior margin entire, nearly trans- 

 verse in the middle, with a shallow notch on each side near the lateral 

 corner. 



Segments with dorsal surface densely hispid with minute sub- 

 capitate hairs, matted with adherent particles of earth; removal of 

 these shows a granular-uneven surface without distinct markings 

 other than the dorsal tubercles and the marginal lobes. Median 

 rows of tubercles as far from each other as from the lateral rows. 



Posterior segments abruptly narrowed from about the seventeenth; 

 the posterior dorsal tubercles distinctly enlarged, those of segments 

 17-19 forming oblique cylindric-conic processes, largest on segment 

 18, those of segment 19 set close together, projecting horizontally. 



Last segment with a short decurved apex distinctly exceeded by 

 the enlarged posterior tubercles of segment 19; dorsal black, rough- 



