NO. 2131. 



NEMATODE PARASITES OF RODENTS— HALL. 



119 



The writer is indebted to Mr. E. K. Warren, of Colorado Springs, 

 for the opportunity to collect this material from alcoholic host 

 material collected by Mr. Warren in 1909 and 1910. The species 

 was tentatively reported by the writer in 1912 as Chahertla species, 



but a subsequent study of the 

 material shows that such 

 structures as the externo- 

 dorsal ray, which originates 

 independently, and the dor- 

 sal ray, which terminates in 

 four substantially e(iual digi- 

 tations, will not permit of 

 placing this form in that 

 genus. 



In passing it may be said 

 that while the writer has fol- 

 lowed Eailliet and Henry in 

 forming tribes on the basis of 

 my formation and the loca- 

 tion and arrangement of the 

 vulva and uteri, the system is 

 not altogether successful in 

 bringing together groups dis- 

 tinctly similar in other re- 

 spects. An arrangement 

 which brings together 



Fig. 146.— Ransomus rodentorum. 

 Portion of male body, .sno'wnNG 

 SPICULES. Enlarged. 



dentorum. 

 Distal ex- 

 tremity of 

 spicule. En- 

 larged. 



,, , , .^, Fig. 147.— Ran- 



iSfrongylus, with a corona somus ro- 

 radiata, and Ancylostoma 

 and Uncinaria^ without a 

 corona radiata and with the 

 rather distinctive hookworm 

 head, as members of the Strongyleae, at the same time placing 

 Cylicostorrhum^ with a corona radiata, in the Cylicostomeae, and 

 NecatoT^ with its hookworm mouth, in the Bunostomeae, is not en- 

 tirely satisfactory. At the same time, Leiper's (1908) division, based 

 on the buccal capsule, and putting hookworms in the Anchylos- 

 tominae, forms with a corona radiata in the Strongylinae, and such 

 forms as Kalicephalus in another unnamed group, is likewise unsatis- 

 factory. The fact that the present grouping is not very satisfactory 

 is one reason for not following other writers who give these groups 

 higher than tribal rank. 



