160 University of California Publications in Zoology [Vol. 20 



In view of the fact that the number, disposition, and specialization 

 of the flagella have been the basis of differentiation in the Poly- 

 mastigina and that the genera of the order are distinguished by their 

 flagellar complexes, it seems to be necessary to establish a new generic 

 name for those species of Trichomonas sensu latu which have only 

 three anterior free flagella. It is necessary to reserve Trichomonas 

 for species with four flagella. 



We therefore propose the new generic name Tritrichomonas for 

 all trichomonad flagellates with the following diagnostic characters: 



Tritrichomonas nom. gen. nov. 



Polymastigote flagellates with three free anterior flagella arising 

 from an anterior centroblepharoplast. This centroblepharoplast gives 

 rise to a posteriorly directed, laterally attached flagellum forming the 

 marginal filament in the sinistral slightly spiral undulating membrane 

 terminating distally in a short free flagellum ; it also gives rise to the 

 paraba.sal body along the base of the undulating membrane, and to the 

 axostyle; cytostome not heavily margined with a deeply staining 

 fibril. We designate the well-known Trichomo^nas augusta Alexeieff 

 as the type species of Tritrichomonas. 



The Genus Giardia 



Giardia Kunstler (1882), pp. 347-349. 



Giardia Kunstler (1883), pp. 52-54, pi. 2, figs. 1-4. 



Dimorphus Grassi (1879), pp. 445-448. Nee Dimorplnis Haller, 1878 

 (Arachnida); nee Dimorpha Jurine 1807 (Hymenoptera) ; nee Dimor- 

 phus Gray 1844 (Mollusca): Hodgson 1841 (Aves). 



Megastoma Grassi (1881), pp. 575-580. Nee Megerle von Miihlfeld (1818) 

 (Mollusca); Blainville 1825? (Mollusca); Swainson 1837 (Aves); 

 Costa 1850 (Pisces). 



Lamhlia Blandiard (1888), pp. 18-19. 



Giardia Kunstler, Alexeieff (1914), pp. 210-212, figs. 4, 5. 



The fir.st description of a species now included in this genus 

 was that of Lambl (1859 nee 1875) of Cercomonas intestinalis from 

 mucus stools of a child. His species is plainly not to be included in 

 the genus Cercomonas. Davaine (1875) described a species belonging 

 to Giardia from the rabbit as Hexamita duodenalis, evidently in 

 ignorance of Lambl 's account, but his species can not be allocated in 

 Hexamitus. 



Gra-ssi (1879) described as Dimorphus muris a species belonging to 

 Giardia from 31 us and Arvicola, and later (1881) from man and the 

 cat. Dimorph%is is, however, a homonym with Dimorphus Haller 



