NEW SPECIES OF (ESOPHAGOSTOMUM. 467 



IS lined with chitin. The ovijectoivs lie in an antero-postevior 

 direction, being however slightly obliquely placed from side to 

 side, Inclusive of its sphincters, it measured, in a 5 15 mm. long, 

 535 jj.. The right uterus terminates in the anterior ovijector ; 

 the terminal portion of the posterior ovijector is bent slightly 

 forward, and the left uterus, which meets it, passes down the body 

 pax-allel to that of the right. 



The eggs (text-fig. Qb) are oval, thin-shelled, and of medium 

 size, measuring on an average 58 X 39 /.t. They commence their 

 development hi utero and, when laid, the embryo has just formed. 



Since writing the above description, I have obtained from 

 nodules in the cascum of a third Ground Squirrel, representatives 

 of a larval stage of 0. xeri, sp. n. These larvae were all females 

 and almost full-grown, being only slightly smaller than the adult 

 forms. From this it would appear that the larval stages, as in 

 several other CEsophagostomes, are also passed inside the tissues 

 of the digestive tract. 



From the above description it is apparent that this parasite 

 belongs to the genus (Esophagostomum ; further, the characters 

 of the mouth capsule and the oesophageal funnel with its 

 armature show that it is closely related to QJ. apiostomum. It, 

 however, differs from (E. apiostomum in two important respects : 

 namely (1) the spicules of the male ai-e much longer, measuring 

 nearly 1300 jj.^ whei-eas in (E. apiostomum thej are less than a 

 millimetre ; (2) the tail of the female is much more abruptly 

 pointed than in (E. apiostoinum ; in the latter the distance from 

 the anus to the tip of the tail is greater than that from the anus 

 to the vulva, whereas in the new form just the reverse is the case. 

 These two characters are constant in all the parasites collected, and 

 may thus be regarded as of specific significance, especially also as 

 these parasites seem to be normal in a host belonging to a group 

 of mammals from which no CEsophagostomes had previously been 

 recorded. For this parasite I propose the name 



CEsojyhagostomum xeri, sp. n., 



with the following specific description : — (Esophagostomuni. Males 

 about 13 mm. and females aboiit 15 mm. long. The maximum 

 breadth of the male is about midway, and is -^ of the total 

 length ; in the female the maximum breadth of about -^-^ the total 

 length is reached at the junction of the posterior and middle 

 thirds of the body. Cuticle transversely striated. Mouth collar 

 about twice as bi"oad as it is deep. Cervical swelling about as 

 long as it is broad. Lateral alse absent. Cervical papillae 

 situated at the level of the anterior margin of the posterior third of 

 the cesophagus. External leaf-crown of 10 elements ; internal leaf- 

 crown small, and of about twice as many elements. CEsophageal 

 funnel well-developed ; its anterior margin thickened, and carrying 

 three recurved tooth-like processes — two subventral and one dorsal. 



