ART. 9. A NEW TKEMATODE FROM WHITE BASS VAN CLEAVE. 7 



arrangement of the oral spines, location of the reproductive orjjjanb, 

 location of the uterus, size of eggs, relative size of the acetabulum, 

 and in many other features the two organisms differ so extremel}'^ 

 they could not be included within the same genus. The superficial 

 resemblances between these two trematodes is of especial interest 

 because their respective hosts are members of the genus Roccus. 



Forbes and Richardson (1908:320) have referred to the similarity 

 in "range, local preferences, feeding habits, and food" of Roccus 

 chrysops and Morone inteirupta. Since Morone interrupta (yellow 

 bass) is the only close relative of R. chrysops in the region under in- 

 vestigation, the writer endeavored to ascertain if this relationship 

 was in any manner reflected in the parasitic fauna of the two species. 

 Not a single specimen of AUacanthochasmus var'ms was encountered 

 in M. interrupta even in regions where R. chrysops was heavily and 

 generally infested by this trematode. The only trematodes encoun- 

 tered in M. inteiTupta belong to an unidentified species, probably of 

 the genus Allocreadium^ though the cuticula is provided with minute 

 spines. This form w^as entirely wanting in R. chrysops. Regardless 

 of their close phylogenetic and ecological relationships these two 

 species of fish display marked diversity in their respective trematode 



faunas. 



SUMMARY. 



1. AUacanthochasmus varius, a new genus and species of trema- 

 todes, is described. 



2. This parasite occurs in the intestine of the white bass {Roccus 

 chrysops) of the Mississippi River and some of its tributaries and 

 from the same host at Sandusky, Ohio. No other host has been en- 

 countered. 



3. Individuals of this species are subject to pronounced variability 

 in form and in relative position of various structures. 



4. The trematode fauna of Morone interrupta^ a near relative of 

 Roccus chrysops, is entirely distinct from that of R. chrysops. 



REFERENCES. 



Forbes, S. A., and Richardson, R. E. 1908. The Fishes of Illinois. Natural 



History Survey of Illinois, vol. 3, St. Lab. Nat. Hist. 

 l.TNTON, E. 1898. Notes on trenuitode parasites of fishes. Proc. U. S. Nat. 



Mus., vol. 20, pp. 507-548. 

 Looss, A. 1899. Weitere Beitrage zur Kenntniss der Trematoden-Fauna 



Aegjptens, zugleich Versuch einer natiirlichen Gliederung des Genus Disto- 



mum Retzius. Zool. Jahrb., Abt. f. Syst.. vol. 12, pp. .521-784. 

 1901. Natura doceri, eine Erklarung und Begriindung einiger 



Grundsiitze, welche mich bei nieinen " Versuche einer natiirlichen Gliederung 



des Genus Distomum Retzius" geleiter haben. Centralbl. f. Bakt., Parasi- 



tenk, u. Infektionskr. Abt. 1, vol. 29, pp. 191-210. 



