233] NORTH AMERICAN MONOSTOMES 15 



During the study of the Cyclocoelidae and the attempt to prepare a 

 key the writer was impressed with the segregation of the genera into dis- 

 tinct groups. These groups are here designated as sub-families. The group 

 composed of Cyclocoelum, Haematotrephus and Hyptiasmus are according 

 to this grouping left in the sub-family Cyclocoelinae created by Stossich 

 (1902) for the entire group. A second group is that formed by Typhlocoe- 

 lum Stossich and Tracheophilus Skrjabin (1913) which on the basis of the 

 strongly developed vitellaria and diverticula of the intestine deserve rank 

 as a distinct sub-family to which I desire to assign the name Typhlocoeli- 

 nae. As stated in a later section of this paper Cohn (1904) would ally this 

 group with the Fasciolidae on the basis of a rudimentary sucker found in 

 Typhlocoelum flavum (Mehlis). A third group is that formed by Ophthal- 

 mophagus and Spaniometra and is based on the position of the ovary in 

 the intestinal arch with the testes anterior thereto, and on the position 

 of the vitellaria which in these genera are ventral to the intestine. Bothrio- 

 gaster is also placed in this group although it presents some striking 

 differences, especially with respect to the vitellaria which in this genus are 

 markedly like those of Cyclocoelum. However with respect to the repro- 

 ductive glands it conforms more nearly to Spaniometra. Other peculiar- 

 ities of this genus will be discussed elsewhere in this paper. 



KEY TO SUB-FAMILIES AND GENERA 



1(11) Ovary between testes or on a level with posterior testis 2 



2(8) Intestinal crura without diverticula 



Sub-family Cyclocoelinae Stossich 1902 .... 3 



3(6) Right and left sides of vitellaria separated at posterior end. . . .4 

 4(5) Uterus loosely folded; long loops surrounding genital glands. . . . 



Haematotrephus Stossich 1902 



5(4) Uterus compact; loops short not surrounding genital glands. . . . 



Cyclocoelum Stossich 1902 



6(3) Right and left sides of vitellaria continuing into one another at 



posterior end 7 



7 Uterine loops extending laterally over intestinal crura and 



vitellaria to body wall Hyptiasmus Kossack 1911 



8(2) Intestinal crura with distinct diverticula 



Sub-family Typhlocoeline .... 9 



9(10) Testes strongly lobed Typhlocoelum Stossich 1902 



10(9) Testes round Tracheophilus Skrjabin 1913 



11(1) Ovary posterior to testes, situated in intestinal arch 



Sub-family Ophthalmophaginae .... 12 



12(15) Vitellaria ventral to crura 13 



13(14) Testes in posterior body half . Ophthalmophagus Stossich 1902 

 14(13) Testes in anterior body half Spaniometra Kossack 1911 



