340 BENEDICT. [Vol. XVI. 



difference then, as well as the size, indicates simply that Leidy's 

 specimens were younger than the ones I studied. The descrip- 

 tion of this form is therefore to be emended as follows : 



Specific Characteristics. — Total length from 280 to 410 mm. 

 Greatest breadth from 1.75 to 2.18 mm. Surface of body very 

 rough, with transverse ridges and furrows. Scolex prominent 

 .^2 to ."^"^ mm. in greatest diameter just behind the posterior 

 margin of the suckers. A minute depression, with a slight 

 elevation in the center, is situated on the rounded apex of the 

 scolex. The suckers are large, directed outward and forward, 

 and separated by deep longitudinal furrows, which continue 

 throughout the length of the short neck. Proglottids closely 

 joined together, with edges very slightly rounded. Immature 

 proglottids much wider than long; majority of proglottids 

 nearly square ; posterior proglottids slightly longer than wide ; 

 last proglottid with a concave posterior margin. Genital sinus 

 irregularly alternate, situated on the margin, one-fourth of the 

 length of the proglottis from the anterior end. Vagina with 

 exceedingly large sphincter muscle and forming a mass of coils 

 immediately anterior to the ovary. Cirrus formed by an in- 

 vagination of the distal end of the cirrus pouch and lined by 

 cuticula continuous with that covering the body. Vas deferens 

 intricately coiled within the pouch and forming a very large 

 complex mass of coils near the center of the proglottis. Excre- 

 tory canals form in the last proglottis a network, which is con- 

 nected with the exterior by a multitude of minute ducts passing 

 through the cuticula. 



General External Morphology. 



The specimens studied were collected by Dr. Ward, while 

 engaged in the biological examination of Lake St. Clair, during 

 August of 1893. During this investigation (Ward, '94) ninety 

 fish of twenty species, caught at New Baltimore on Lake St. 

 Clair, were examined. Half of them proved to be free from ces- 

 todes, while the remaining contained two hundred and twenty- 

 seven specimens of several species. All of the six individuals 

 of Micropterus dolomieu examined were found to be infested by 



