176 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.42. 



Washington from Montana. This specimen he had been unable to 

 identify with any described species. Examination shows that it is 

 of the same species as that collected by us in Colorado. Ostertagia 

 lullosa is therefore known to occur in two of the Rocky Mountain 

 States. Two other species of this genus have been found thus far only 

 in the Rocky Mountain region, namely Ostertagia marsliaUi and 0. 

 occidentalis, these two being reported heretofore only from Montana. 

 To these records may be added our finding, in 1911, at a Denver 

 abattoir, of 0. marshalli in sheep from Wyoming and Utah, and of 

 0, occidentalis in sheep from Wyoming. 



The new species is white when freshly collected and has the usual 

 characteristics of the genus Ostertagia, but differs from other species 

 of the genus in that the two ventral rays of each lateral lobe of 

 the bursa are rather widely divergent, the spicules are simple and 

 not spUt into several processes posteriorly, and the gubernaculum 

 is of the same yellow-brown color as the spicules instead of being 

 colorless. 



In the key given in Ransom (1911) this species runs down to 

 Ostertagia trifurcata of which only the male is known. In several 

 respects, however, it differs from trifurcata. The gubernaculum in 

 0. trifurcata is a narrow colorless structure, whereas in 0. huUosa it is 

 a yellowish-brown structure, irregularly trihedral in shape. The 

 spicules in 0. trifurcata are twisted but are not curved in their long 

 axis, and are divided into 3 processes at the posterior end. The 

 spicules in 0. lullosa are narrow, curving, tubular structures, not 

 divided at the posterior end which is acutely pointed. Each of the 

 two terminal branches of the dorsal ray in 0. trifurcata has a short 

 process on the outer side and one on the inner. 0. bullosa has a short 

 process on the outer side, but the process on the inner side is only sug- 

 gested by a shght and often indistinct bifurcation at the tip. 



The principal characters of 0. bullosa are as follows: 



OSTERTAGIA BULLOSA Ransom and Hall, 1912. 



Specific diagnosis. — Ostertagia: Male (fig. 1) about 7.3 mm. long. 

 Maximum thickness 115 /« just in front of bursa. Diameter of head 

 17 fi; diameter of body at level of nerve ring 44 to 48 //, at base of 

 esophagus 68 pi. Esophagus 510 to 545 //in length, surrounded by a 

 nerve ring at a distance of 220 to 250 /x from the anterior end. The 

 excretory pore is situated about 270 fi from the anterior end of the 

 body. Cervical papillae not evident. The esophagus increases in 

 diameter from 16 pi anteriorly to 45 or 50 // at its posterior end. The 

 bursal membrane has a very distinct longitudinal striation. The 

 median lobe is only slightly shorter than the lateral lobes. The lateral 

 lobes are usually partly folded over each other in their ventral por- 

 tions. The ventro-ventral (fig. 2, v. v.) and latero- ventral (fig. 2, 1, v.) 



