Parasites of skates (Trigonidae). 



The type and only genus, Dasybatotrema Price, 1936. 



Unfortunately we did not possess the material on the single known 

 species, D. dasybatis (MacCallum, 1916); however, on the basis of a suf- 

 ficiently good description of this form in the work of Price (Price, 1938a) 

 we can conclude that this species deserves to be isolated not only into a 

 special genus but also into a special subfamily which occupies an inter- 

 mediate position between Monocotylinae and all remaining subfamilies. 

 Thus, the basic characteristic which unites Dasybatotrema with Mono- 

 cotylinae is the presence of a single vagina, whereas among the remaining 

 subfamilies it is double. Conversely it will also have in common with the 

 latter the reduction of the posterior middle septa of the attaching disc as 

 well as special structure of the middle hooks. In Dasybatotrema these hooks 

 do not have an internal extension but only a small inflation which remains in 

 Its place and this inflation corresponds not to the internal extension, but 

 rather to the widening of the basal part of the middle hooks of the dactylogyrid- 

 type (see Fig. 276, C). Such a dasybatotremid-type of hook encountered in 

 the present group is known only in one of the genera of Monocotylinae 

 (Spinurus) and is characteristic, with small variations in shape, for 

 Calicotylinae and Merizocotylinae. Taking into consideration what has been 

 said and also that the species examined differs from Calicotylinae by a single p_ 359 

 testis whereas in the latter subfamily there are many of them, and in 

 addition to that, by the considerable differences in the structure of the 

 attaching disc from the one among Merizocotylinae, we consider it quite 

 legitimate to establish the independent subfamily of Dasybatotreminae 

 which stands between Monocotylinae and Calicotylinae in the system. 



3. Subfamily Calicotylinae Monticelli, 1903 



(Figs. 81, 101, D, 274, C, 277) 



Monocotylidae having an attaching disc with a central depression 

 and 7 peripheral ones delineated from each other by muscular septa. As 

 an exception the primary depressions and septa which are located in their 

 usual sites on the disc can disappear and in their places numerous smaller 

 depressions lying in disorder and delimited from each other only by the 

 elevation of the tissue of the disc and not by special septa can be formed 

 (Dictyocotyle). The anterior end with a developed adoral sucker and a 

 number of cephalic glands. The eyes exist (always ?), two pairs, among 

 adult animals, acquiring (always ?) the shape of two elongated longitudinal 

 bands. The vaginal ducts are paired. The testes are follicular, numerous. 



439 



