136 BULLETIN 168, UNITED STATES NATIONAL MUSEUM 



Plate 24 

 Proisotoma {Proisotoma) immersa: 



262. Dorsal aspect of head, X 230. 



263. Eyes and postantennal organ of right side, X 673. 



264. Dorsal aspect of left antenna, X 427. 



265. Sense organ of third antennal segment of right side, X 1,640. 



266. Ventral aspect of anal lobes, X 1,280. 



267. Right hind foot, X 960. 



268. Left mucro, X 927. 

 Proisotovia (Proisotoma) constricta: 



269. Postantennal organ and adjacent eyes of right side, X 673. 



270. Sense organ of third antennal segment of right side, X 1,067. 



271. Left hind foot, X 673. 



272. Left mucro, X 1,067. 

 Proisotoma {Proisotoma) cognata: 



273. Left postantennal organ and adjacent eyes, X 407. 



274. Right hind foot, X 673. 



275. Left mucro and end of dens, X 850. 



Plate 25 

 Isotomurus retardatus: 



276. Eyes and postantennal organ of right side, X 347. 



277. Left fore foot, X 373. 



278. Right hind foot, X 373. 



279. Left mucro, X 640. 



280. Spinulate seta from abdomen, X 680. 

 Isotomurus palustris: 



281. Typical form, X 40. 

 Isotomurus palustris texensis: 



282. Specimen, X 45. 



283. Specimen, X 46. 



Plate 26 

 Isotomurus palustris: 



284. Eyes and postantennal organ of right side, X 340. 



285. Right hind foot, X 560. 



286. Left hind foot, X 407. 



287. Left mucro, X 853. 



288. Dorsal aspect of left mucro, X 1,120. 



289. Left aspect of tenaculum, X 333. 



290. Spinulate seta from fourth abdominal segment, X 673. 

 Isotomurus palustroides: 



291. Eyes and postantennal organ of left side, X 173. 



292. Postantennal organ and adjacent eyes of left side, X 393, 



293. Right hind foot, X 393. 



294. Left mucro and end of dens, X 673. 



295. Dorsal setae of second abdominal segment, X 513. 



Plate 27 

 Isotoma (Pseudisotntna) sensibilis: 



296. Eyes and postantennal organ of right side, X 473. 



297. Right hind foot, X 1,120. 



298. Left mucro, X 1,067. 



299. Right mucro, X 960. 



