64 ILLINOIS BIOLOGICAL MONOGRAPHS [344 



state that the oral sucker is wanting and describe the anterior sucker as 

 the pharynx, notwithstanding the arguments of Pratt (1900), Looss 

 (1902) and Stiles and Goldberger (1910) that the anterior sucker of the 

 amphistomes is homologous with the oral sucker of the distomes. 



The material of this family available for the present study consisted 

 of representatives of two species from North American turtles, and an- 

 other species from the duck, Anas platyrhynchos. A study of the liter- 

 ature showed that these forms could not be included in any previously 

 described genera. 



THE GENUS ALASSOSTOMA 



A new genus Alassostoma is formed to include the two species from 

 turtles. The genus is characterized by the presence of large oral evag- 

 inations which open independently into the oral sucker, an esophageal 

 bulb composed of concentric muscle lamellae, a hermaphroditic duct, 

 germ glands near the middle of the body in the median line, both testes 

 anterior to the ovary, vitellaria consisting of small scattered follicles in 

 the lateral, and posteriorly in median areas of the body, Laurer's canal 

 opening in the mid-dorsal line anterior to the opening of the excretory 

 vesicle. Alassostoma magnum is to be taken as type of the genus, and 

 in it is included also the new species A. parvum. 



The genus Alassostoma has the type of lymph and excretory systems 

 present in the genus Schizamphistoma and designated by Looss as char- 

 acteristic of the subfamily to which that genus belongs. Looss (1912) 

 predicted that with the discovery of other forms it would be necessary 

 to create a new subfamily to contain them, and at that time stated the 

 subfamily characters. With the discovery of a second genus, so similar 

 to Schizamphistoma that the two must be included in the same subfamily, 

 the formal recognition of the new subfamily is necessary. Schizamphis- 

 toma Looss was designated as type and the name of the subfamily be- 

 comes Schizamphistominae. The subfamily contains the genera Schiz- 

 amphistoma, including also S. spinulosum which as already indicated by 

 Looss and discussed in this paper is tj'pe of a new genus, and the genus 

 Alassostoma. The distinguishing characters of the subfamily as stated 

 by Looss are two long excretory vesicles which extend singly to the an- 

 terior end of the body and a lymph system composed of three canals on 

 either side of the body which run longitudinally and break up into many 

 sinuses in the regions of the suckers. 



Comparisons. — When one compares the species A. magnum, and A. 

 parvum with descriptions in the literature, they are seen to agree most 

 closely with Schizamphistomum scleroporum and S. spinulosum Looss. 



