BY T. HARVEY JOHNSTON AND O. W. TIEGS. 89 



able in that it is connected by a wide opening with the cavity of the intestinal 

 limbs (PI. ix., fig. 3).* 



The uterus does not contaia more than one egg. The latter is almost 

 spherical and is provided with a large spime, measuring about .025 mm. in 

 diameter. 



Found, generally in pairs, on the giUs of Therapon carbo Ogilby and 

 McCuIIoch, and T. Mill Castelnau from the Thomson Eiver, Longreach, Central 

 Queensland. 



2. T Ri V ITELLIN A, n.gen. 



Protogyrodactylidae, rather longer than broad; clasping disc sharply marked 

 ofE from the body and not strongly "padded," bearing four very large, and 

 twelve minor hooks, the latter rather larger than usual; three pairs of "head- 

 organs"; oesophag-us absent; limbs of the intestine united posteriorly; four 

 eyes; beside the anterior yolk system, there are two posterior systems, one of 

 Avhich is connected with the intestine. 



Found on the gills of freshwater fishes. 



Type species, Trivitellina subrotunda J. & T. 



Trivitellina subrotunda, n.sp. (Plate x., fig. 7.) 



This minute organism, measui'ing about .2 mm. in length and .18 mm. in 

 greatest breadth, is a short, thickset parasite with lateral, somewhat wing-like 

 expansion, and, except for the presence of the disc, is almost circular in shape. 

 The posterior two-thirds of the worm generally lie wt'U beneath the surface of 

 the gill-filament, only the anterior third protruding. The disc projects backward 

 and is sharply marked off from the rest of the body, differing in this respect 

 from Protogyrodactylus. 



The curious "padding tissue" characteristic of the last-named is absent, 

 but seems to be represented by a modified parenchyma present at the posterior 

 end of the animal and consisting of three paired masses, with a smaller mass 

 between them. The anterior masses approach the intestine, while the posterior 

 lie within the disc and are closely related to the small hooks on it. 



The disc is proportionally large and its posterior part is ornamented with 

 curious chitin-pieoes. Four large hooks are present, the dorsal pair being the 

 smaller, and each of the four is supported by a small chitinous rod, giving the 

 hook a triradiate appearance. The posterior hooks are very large and strongly 

 curved outwards, their bases being connected by a transverse bar. The base of 

 each large hook articulates with a small triangular chitin-pieee into which the 

 muscles of the hook are inserted. Each is supplied with a pair of muscles: (1) 

 the longitudinal musculature of the body, which runs forward as far as the 

 pharynx, and (2) a small transverse muscle, which arises from the ventral por- 

 tion of the disc. The latter is armed also with six pairs of rather large 

 secondary hooks whose distribution is shown on Plate x., figure 7. 



•The presence of a communication between the female system and the intestine lias 

 been described by Ijima as occurring in certain monogenetic Trematodes ( Polystotnum , 

 Diplozoon, Octobothrium). Von Graii found two such connections in the land Planarian, 

 Rhynchodemus, and one in Pelmatoplana ; Bendl (Zool. Anz., 35, 1909, p. 294) found one 

 to occur in the Khabdocoele, Phaenocora, while Haswell discovered a genito-intestinal canal 

 in the Polyolad, Enterogonia pigrans. 



Professor Haswell has recently drawn our attention to a paper by Merton (Zool. Anz., 

 4,1, 1913, p. 413) in which a remarkable organ called "vesicula resorbiens" by him, is 

 described as lying in the wall of the intestine of Teinnotcphala setnperi, into which it may 

 apparently open at intervals, the organ communicating directly with the female ducts. 



