270 ILLINOIS BIOLOGICAL MONOGRAPHS [270 



Tetracotylus hdd been used in place of Tetracotyle. For these reasons 

 the name Ichthyotaenia should be used in place of it. 



La Rue (1911:474) established for this and certain other species the 

 genus Monticellia and the family Monticellidae. 



This study is based upon data secured from Monticelli's (1891) 

 paper and also upon Monticelli's type slides which Professor H. B. 

 Ward very kindly secured for study. This material originally came 

 from the zoological museum at Vienna. The host of the species is Silu- 

 rus sp. 



Monticelli (1891) is quoted on the external characters for the 

 writer has examined only prepared slides of this species: 



"Capo slargato subtriangolare, visto di fronte, rigonfiato, subquadrato, ante- 

 riormente allunganto a formare un cocuzzolo conico, inerme, non molto proeminente, 

 ben distinto dal collo. Le quattro ventose mediocri non molto proeminenti, disposte 

 ai quattro angoli del capo. Collo lunghissimo, ristretto. Prime proglottidi brevi, 

 mediane subrettangolari, posteriori ed ultime decisamente rettangolari, rigonfie nel 

 mezzo. Aperture genitali marginali irregolarmente alternanti." 



Monticelli (1891) gives no dimensions of the head, neck and strobila. 



One of Monticelli's slides showed the head of Tetracotylus corypki- 

 cephala in toto. This head which had been badly compressed and 

 somewhat broken by that treatment measured 0.459 mm. broad. This 

 dimension, however, is too great and it seems that the normal head 

 would not measure over 0.35 or perhaps 0.375 mm. The head should be 

 described as somewhat globose rather than sub-triangular. The suckers 

 could not be measured except in length which was about 0.150 mm. 

 Monticelli's drawing of the head (Fig. 132) shows that the suckers are 

 irregularly oval in shape, the longitudinal axis of the suckers being the 

 greater. The neck in this slide was too badly crushed to permit accurate 

 measurement. It was cut off 3 or 4 mm. from the head and showed no 

 traces of segmentation. No young proglottids were to be found in the 

 slides examined by the writer. Four representative ripe proglottids 

 were measured. Their dimensions were 1.95 mm. broad by 0.68 mm. 

 long, 1.85 by 0.75 mm., 2.0 by 0.75 mm., 1.80 by 1.0 mm. Transections 

 of ripe proglottids are about 0.34 mm. thick. The proglottids are at- 

 tached by their full width. The angles of the segments can scarcely be 

 seen and the intersegmental furrows are very shallow. These observa- 

 tions were made on a limited amount of material so it is possible that 

 some of the statements just made would require modification if consid- 

 erable good material could be examined. 



The genital pore (Figs. 95, 186) is marginal, irregularly alternat- 

 ing and situated at the end of the first one-fifth to one-fourth of the 



