4 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. C5. 



In Looss's drawing (Looss, 1911, fig. 116) of the bursa of JJ . crlni- 

 jormis the postero-lateral ray is shown as thicker than the medio- 

 lateral ray. In all the specimens I have examined the reverse is true 

 (fig. 10). 



The lateral membranous ala of the spicule is more strongly de- 

 veloped in U. criniformis than in U. stenocephala and extends 

 around the tip. In U. stenocephala it narrows down and disappears 

 before the tip of the spicule is reached. 



In the specimens that I have examined, the cuticle of Uncinarla 

 stenocephala is usually considerably thicker than that of U. crini- 

 formis. For example, on the tail of the female of the latter species 

 it has not been found to exceed 5 [a in thickness, but commonly 

 measures 7 or 8 [jl in thickness in the same region of the female of 

 U. stenocephala. 



In both U. a^niformis and U. stenocephala the excretory pore, 

 nerve ring and cervical papillae are located in the same general 

 region of the neck, but vary more or less in their relative positions in 

 different specimens in both species. I have failed to find constant 

 differences in these characters between the two species. 



The caudal pores on the tail of the female are about 45 [x from the 

 tip (excluding the caudal bristle) in U. stenocephala, and in the 

 only case measured in U. cinnifo^'mis were 30 [i from the tip. 



It is of interest to note that as yet Uncinaria stcTwcephala is not 

 known to have become established as a parasite of the dog in the 

 United States except in Alaska. On the other hand it is a common 

 parasite of the foxes on fur farms in the Northern United States, 

 including Alaska and in Canada, and is one of the most serious pests 

 with which fox raisers have to contend. Thus far, the only cases 

 of this parasite in dogs in North America of which I have knowledge 

 are those seen by Hadwen in Alaska. The same observer has found 

 U. stenocephala in a hog at Ottawa, Canada (Ransom, 1921, p. 190). 



ADDENDUM. 



While the present paper was in the hands of tlie printer two 

 papers, one by Fiilleborn (1924) and one by Cameron (1924) have 

 appeared which bear upon the question of the identity' of Unchuiria 

 polcn'is and U. stenocephala. Both authors are of the opinion that 

 the two forms belong to the same species, an opinion which accords 

 with my own findings based upon a study of the material from 

 which Looss obtained his specimens of U. polaris. Cameron appears 

 to be doubtful whether the fonn described by Goeze as Ascai^s 

 crinifarnvis should be considered an identifiable species. In view 

 of the fact, however, that a well-defined species of Uncinaria occurs 

 in the European badger which seems in all probability to be the 

 same as that described by Goeze there appears to be no good reason 



