24 PROCEEDINGS OF THE NATIONAL MUSEUM vol.88 



HETERAXINE, new genus 



This trematocle agrees with the genus Microcotyle in having nu- 

 merous suckers in two longitudinal rows on the posterior sucker- 

 bearing portion, but differs from that genus in having the suckers of 

 one of the rows fewer and much larger than those in the other row. 



Type species. — Heteraxine cokeri^ new species. 



HETERAXINE COKERI, new species 

 Plate 17, Figuees 231-233 



Body stoutish, tapering slightly to a rounded point at the anterior 

 end; posterior sucker-bearing portion with two parallel rows of 

 suckers, the one on the right side containing about 10 large suckers, 

 the one on the left side with 30 or more small suckers. All the 

 suckers are supported by a chitinous framework. Length in balsam, 

 about 5 mm.; breadth, 1 mm. One of the large suckers measured 

 0.23 mm. in length and 0.35 mm. in breadth ; one of the small suckers, 

 length, 0.08 mm., breadth, 0.14 mm. Length of anterior suckers, 

 0.1 mm., breadth, 0.06; pharynx, length, 0.09 mm., breadth, 0.07 mm.; 

 esophagus very short; genital aperture a short distance back of 

 pharynx, at forking of intestine; retracted cirrus with a fascicle of 

 slender spinelike hooks. These hooks are arranged in two circles, 

 an outer with hooks 0.045 mm. in length and an imier with hooks 

 0.12 mm. in length. The ovary, as much of it as could be made out, 

 which is the part that contains large, nucleated cells, begins on the 

 left side of the median line, goes forward a short distance, crosses to 

 the outer side, then turns posteriorly, and immediately returns to 

 the median line, or a little to the left of it. Two main vitelline ducts 

 unite in a single short vessel on the ventral side of the ovary. It was 

 not possible to determine the exact number of testes, on account of 

 the irregular shape and lobed character of some of them. The num- 

 ber appeared to be about 30. The vitellaria extend from about the 

 level of the genital opening to near the posterior end of the sucker- 

 bearing portion. An ovum in the uterus measured 0.3 mm. in length, 

 exclusive of the long filament at the anterior end, and 0.08 mm. in 

 diameter; another measured 0.4 by 0.11 mm., exclusive of the anterior 

 filament. 



Type specimens. — U.S.N.M. No. 8169 (holotype and paratypes) 



Host. — Fresh-water drmn {Aplodinotus grunniens). 



Record of collection, — Two (U.S.N.M. No. 8169) received from 

 Dr. R. E. Coker, Fairport, Iowa, No. 360 Meek Collection, May 

 2, 1913. 



