The present family is removed by us from Trochopodinae, in the 

 old understanding of the latter, on the basis of the structure of the 



attaching disc which in Megalocotylinae, pertains to the first of the types 

 which were analyzed above and among Trochopodinae (s. str. ) to the second. 

 In spite of the fact that both subfamilies are very close in the rest of their 

 characteristics, we consider these differences to be of primary importance. 



As regards the genus Megalocotyle, as we have already mentioned 

 earlier (see page 258 ), M. rhombi (Beneden and Hesse) and M. squatinae 

 (MacCallum), must be excluded from it without any doubt. The last species, 

 attributed to the genus Megalocotyle by Price in 1939, was redescribed by him 

 somewhat earlier (Price, 1937b) from samples collected in Singapore fronn 

 the gills of Squatina squatina (L. ) by MacCallum's son back in 1916. The 

 very inaccurate first description of MacCallum was made on the basis of 

 these collections. The attaching disc of this form has a much more complex 

 structure than among all Megalocotyle while retaining the same basic type 

 of structures. As is apparent from Fig. 279, 2 of the septa are subdivided 



each into 3, forming 4 more supple - 

 nnentary depressions and in addition 

 to that, in the posterior depression 

 of the disc there are inceptions of 

 2 incomplete septa, and in both of 

 the anterior ones, one each. Thus, 

 we see here the process of compli- 

 cation analogous to that of 

 Monocotylidae although, it is true, 

 proceeding along more complicated 

 lines. This characteristic can be 

 considered sufficient for separation 

 of this species into a special genus; 

 however, the cephalic end of these 

 worms also has a special structure 

 which also is of important systematic 

 significance. In general traits the 

 anterior end of M. squatinae has the 

 same structure as in Pseudobenedenia, 

 i.e., the anterior edge is equipped 

 with glandular preoral lobes and two 

 more or less strongly developed 

 suckers. All this taken together 

 allows us to consider it necessary to isolate M. squatinae into a special 

 genus--Sprostonia Bychowsky, gen. nov. so far with a single species 

 S. squatinae (MacCallum, 1921) Bychowsky comb. nov. ^ 



Fig. 279. Sprostonia squatinae 

 (MacCallum) adult worm. 

 (According to Price, 1937). 



The genus is named in honor of N. Sproston^who in her resume^ 

 (Sproston, 1946) first pointed to the dubiousness of the attribution of 



4.50 



