48 ILLINOIS BIOLOGICAL MONOGRAPHS [328 



Cotylaspis cokeri has been mentioned but once in print, but on the 

 basis of extended studies this form had been fully described and its 

 position as a new species demonstrated in a thesis submitted by the 

 writer in partial fulfillment for the degree of Master of Arts in the 

 Graduate school of the University of Illinois in June 1914. The fol- 

 lowing October Barker and Parsons (1914), having also been working 

 on this form independently, published a brief description naming it 

 Cotylaspis cokeri. Since I had completed my work on it before the 

 appearance of their note and the publication of their final report has 

 been delayed it seems proper to give here a detailed description of the 

 species. 



ASPIDOGASTER CONCHICOLA von Baer 1827 



About fifty specimens from the pericardial and renal cavities of 

 Andonta corpulent a from Havana, Illinois, and a similar number of 

 specimens from the same organs of Quadrula undulata from North 

 Judson, Indiana, constitute the material of this species available for 

 study. 



A detailed comparison of these specimens with the descriptions of 

 A. conchicola as given by Voeltzkow (1888), Stafford (1896), and other 

 writers, shows that they belong to that species and substantiates the obser- 

 vations of Leidy (1851), Kelly (1899), and Kofoid (1899), that A. con- 

 chicola occurs in this country. So far it is the only species in the genus 

 known from molluscan hosts. 



Kelly (1899) made a parasitological examination of 1537 individ- 

 uals of forty-four species of unios from Mt. Vernon, Iowa, Havana, 

 Illinois, and Lewisburg and Phoenixville, Pennsylvania, and included 

 in his report results of the examination of seventy-seven individuals 

 belonging to eighteen species, made by Kofoid in 1895 and 1896. In 

 four hundred thirty-five cases A. conchicola was found in the pericar- 

 dium only, in seventy-five in the kidneys only, and in one hundred 

 thirty-four cases both cavities contained the parasite. The presence of 

 the mature trematode in the pericardium and of eggs within the nephri- 

 dia was not infrequent. Of the 1537 specimens examined, forty-one 

 per cent were parasitized with A. conchicola and thirty-seven of the 

 forty-four species were infested with the parasite. 



No further data on this species were obtained by the present study. 



