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PEOCEEDIlirGS OF THE NATIONAL MUSEUM 



VOL. 79 



wide, situated between the testes and separated from them by the ter- 

 minal portions of the ceca. Shell gland well developed, lying im- 

 mediately in front of the ovary. The uterus runs forward in regular 

 transverse coils and terminates in a poorly defined metraterm which 

 is about one-half the length of the cirrus pouch. The vitellaria 

 are extracecal and extend from the anterior margin of the testes to 

 the level of the base of the cirrus pouch. Eggs slightly asymmetri- 

 cal, 18fi to 20/A long by lOfi wide, provided with a filament at each 

 pole. 



Host. — Ondatra zibethica. 



Location. — Large intestine. 



Distribution. — United States (Maryland). 



Type specimens. — ^U.S.N.M. Helm. Coll. No. 29726; paratypes 

 No. 29727. 



Specimens of this species were collected by Dr. G. Dikmans from 

 the same host viscera in which the two preceding species, Echino- 

 chasinus schwartzi and Vrotretna shillingeri^ were found. 



In addition to the one species described here, the genus Para- 

 monostomum contains three species, P. alveatum Mehlis (in Crep- 

 lin, 1846), P. ionorne Travassos, 1921, and P. echinum Harrah, 1922. 

 Of these species, P. psevdalveatuin resembles P. alveatum more 

 closely than it does either of the other species. It differs from P. 

 alveatum chiefly in its smaller size and in the extent of the vitel- 

 laria, which in P. alveatum extend anteriorly to about the equator 

 of the body while in P. psevdalveatum they extend to the level of the 

 base of the cirrus pouch. 



The following table gives the essential measurements and other 

 characters of the species that have been included in the genus : 



