BY S. J. JOHNSTON. 337 



tal pore, the disposition of the genital glands, the character 

 of the cirrus-sac and related parts,* the presence of a recep- 

 taculum seminis and Laurer's canal, and the disposition of 

 the yolk-glands and the uterine loops, it agrees with the sub- 

 family as defined by Looss(50, p. 607), the only important 

 differences being in the relatively considerably longer, though 

 still short, intestinal limbs in Mesocoelium, and its tubular 

 excretory vesicle, the Brachycoeliinae being stated to have a 

 V-shaped excretory vesicle. But the excretory vesicle of M. 

 mesembrinum, in which species I have studied it most closely, 

 19. f ^cactly of the type of vesicle described by Looss (55, p.815) 

 for Brachi/creliiim crassicoUe, with its incipient bifurcation at 

 its anterior end (Fig. 71). 



In other respects besides this excretory vesicle, e.g., in the 

 characters of the cirrus-sac and related parts, in the character 

 of the skin and suckers, position of the genital pore, disposi- 

 tion of the genital organs, etc., Mesocoelium appears to be 

 more closely related to Brachyccelium crassicolle than to the 

 other members of the suborder. I have been in doubt 

 whether, on account of the character of its excretory vesicle 

 (the relative length of the intestine is not of much import- 

 ance in discussing differences of subfamily rank), Mesocoelium 

 can properly be included with the Brachycoeliinae as defined 

 by Looss, but it must certainly be placed very close to 

 Brachyccelium, crassicolle, and go into the same subfamily with 



* Ltihe, in his account of Distomum socia/e (60, pp. 171-173), doea not 

 mention the cirrus-sac and related parts, though he says in a footnote : 

 " Dass Lerithodtndrinm craa^iiroUe einen typischen, nuiskulosen Cirrus 

 beutel hesitzt, ahnlich demjenigen der Dicrocoelien, habe ich kiirzlich 

 auch noch an lebend untersuchten Exemplaren sicherstellen konnen." 

 But in all its structures described, D. sociafe is so closely related to the 

 three species described as new in this paper, that I am taking it for 

 granted that the structure of those parts also closely corresponds to that 

 of its Australian representatives. 



