MILLIPEDS OF PANAMA—LOOMIS 107 
Segment 2 with sides curving forward and extending considerably 
lower than either segment 1 or 3; it and ensuing segments to caudal 
end of body with anterior and posterior corners of lateral carinae 
rounded, the posterior ones of segments 16 to 19 somewhat angular; 
carinae thick, narrow, continuous with the descending dorsum and all 
curving forward noticeably except on caudal segments. Last segment 
with apex narrowed and decurved, surpassing the valves. 
Legs not noticeably long or slender, the last pair with a slender 
seta at the outer dorsal end of joint 5 that is longer than joint 6 (fig. 
6a); similar setae rapidly decreasing in length are on the fifth joints of 
legs immediately in front of the last pair. 
Family Strongylosomidae 
Genus Mestosoma Silvestri 
Mestosoma Silvestri, Boll. Mus. Anat. Comp. Torino, No. 283, vol. 12, p. 3, figs. 
1-5, 1897. 
Nearctoma Chamberlin, Ann, Ent. Soc. America, vol. 45, p. 582, fig 46, 1952. 
Typsr Species: N. cuzconum Chamberlin. 
Mestosoma isthmianum, new species 
Figure 6b 
Houotype: Male, USNM myriapod collection 2646, Alahjuela, 
Panama, July 20, 1923, H. F. Loomis. 
AuLoTyPE: Female, USNM, same collection as for holotype. 
ParatypEs: Male and female, author’s collection, same collection 
data as for holotype. Canal Zone, several males and females from 
Balboa, Paraiso, and Pedro Miguel, July 1923, O. F. Cook and R. D. 
Martin. 
Dracnosis: Related to M. araguanum (Chamberlin) from Venezuela 
as indicated by the gonopods but differing in certain details and in 
having the dorsum smooth and shining, instead of irregularly rough- 
ened as in that species. 
Description: Length 25 to 27 mm., width 2.5 to 3 mm.; males 
more slender than females. 
Body smooth, strongly shining; each segment with four setae near 
the anterior margin except on last segment, which has them near the 
middle with another series of four just in front of the apex; segment 
1 also has an additional seta on each side of the middle at the posterior 
third. Color in alcohol nearly black throughout except for a broad 
longitudinal median yellowish-brown stripe extending from the anterior 
margin of segment 1 to the produced apex of the last segment; head, 
antennae, and anal valves wholly black; preanal scale yellow. 
