1. Subfamily Monocotylinae Gamble, 1896 



(Figs. 27, 48, 72, 80, A, 94, 274, B, 275) 



Monocotylidae, having an attaching disc with a central depression 

 and 8 peripheral depressions delimited from each other by muscular septa. 

 The anterior end of the body has 2 lobes into which cephalic glands open 

 and has a weakly developed one adoral sucker. The eyes exist or are 

 absent (?). The vaginal duct is single. The testis is single or divided 

 into three parts. 



Parasites of skates, Trigonidae, Rhinobatidae and Myliobatidae, 



Type genus, Monocotyle Taschenberg, 1878. 



Here belong in addition- -Heterocotyle Scott, 1904 and Spinurus 

 Doran, 1953. 



The absence of eyes among a part of the representatives of the 

 subfamily indicated above (with a question mark) is apparently erroneous and 

 these data are based on inaccurate observations. All the species which 

 have been studied more carefully appear to have two pairs of small but fully 

 developed eyes. There is no doubt that the genus Heterocotyle is more 

 primitive than the type genus of the subfamily. Thus, their basic differences 

 can be reduced to the presence among the first of the usual rounded testes 

 and among the second of a testis subdivided into three unequal parts. It 

 seems to us erroneous to consider that Monocotyle has three testes as is 

 usually indicated because Goto describes one seminal duct among M. ijinne 

 Goto, which shows that the initial presence of a single testis (Goto, 1894) 

 is apparently right. The drawing of Palombi (Palombi, 1942a) in which a 

 separate canal, which fuses somewhat further anteriorly, emerges from 

 each of the front testes arouses doubt, for without resorting to sections, 

 these ducts are very difficult to see and the drawings of Palonabi are often 

 excessively schematic and often very inaccurate. Consequently^it is probable 

 that the picture represented by Goto is more likely since the phenomenon 

 of fragmentation of testes without formation of separate seminal ducts is 

 widely distributed among many monogenetic trematodes. 



The structure of the attaching disc among the single species 

 of Spinurus, S. lophosoma Doran (Doran, 1953), is of special interest. In p. 368 



the disc of the species, which is of the type customary to the subfamily, in 

 addition to the normal armature there are special odd-shaped chitinous 

 thorns located in two rows. The first row>consisting of 8 smaller thorns, 

 lies near the posterior edge of the disc and the second of 6 larger thorns 

 is closer to the central depression of the disc. The edges of all the thorns 

 face the anterior end of the body (Fig. 275). Thus, one observes a con- 

 siderable similarity between these formations and the thorns of 



437 



