MONOCOTYLE FLOR1DANA, A NEW MONOGENETIC TREMATODE. 



By Hexry S. Pratt. 



The genus Monocotyle was established by Taschenberg, in 1878, for 

 a worm which he had found on the gills of the eagle-ray (Myliobatis 

 aquila) at Naples, and which he named Monocotyle myliobatis. The 

 only other known species is Monocotyle ijinice, which was discovered in 

 Japan in the mouth of Trygon pastinacea, and described by Goto in 

 1894. The worm herein described makes the third member of the genus 

 and was taken from the gills of the whip-ray (Myliobatis freminvillei) in 

 the Gulf of Mexico and studied at the Marine Biological Laboratory of 

 the Carnegie Institution of Washington at Tortugas, Florida. It differs 

 in certain features from the two other species of the genus, but in the 

 general shape and size of the body, the form and structure of the suck- 

 ers, down to the smallest details, and the general arrangement of the 

 genital organs it shows a close relationship to them, especially to M. 

 ijimoi. M. aquila is not well known anatomically. Its male genital organs 

 have not been seen at all and the descriptions of the female genital tract 

 are not complete. 



The body of Monocotyle floridana is elongate and thin, being convex 

 dorsally and flattened ventrally. A large individual, selected for descrip- 

 tion, measures 1.3 mm. in length and 0.58 mm. in width in the widest 

 place, which is just back of the middle, and is about half as long as the 

 Japanese and a third as long as the Mediterranean species. From the 

 widest point the body tapers towards both ends. The anterior end is 

 usually more or less truncated, as in M. ijimce, and also possesses the 

 sticky glands which characterize that species. These glands (fig. 2) are 

 four in number and are dorsal in position, lying embedded in the muscle 

 of the oral sucker; but instead of being near the surface or at the for- 

 ward end of the body, they are situated at a considerable distance from 

 the forward end, as is also the case in the closely allied genus Calicotyle, 

 being dorsal to the brain, and are joined with the forward end of the 

 body by long sinuous ducts. Each gland is irregular in shape and about 

 0.03 mm. long, while its duct has a length of about 0.17 mm. 



The mouth is a large funnel-shaped opening, subterminal in position , 

 0.10 mm. in diameter and 0.12 mm. deep. It is surrounded by a lip-like 

 projection which forms a slight flange posteriorly and laterally and 

 which extends forward anteriorly and dorsally beyond the end of the body 

 (figs. 1,2, and 3, /.). This lip is non-muscular and apparently receives 

 the secretions of the four glands just mentioned. Surrounding the 



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