112 NEW GYRODACTYLOID TEEJIATODES FROM AUSTEALIAX PISHES, 



and vaginal apertures, to open beside the eirras sac. Its anterior half is lined 

 with chitin and is therefore very clearly visible. The vagina travels forward 

 after joining the narrow uterus and close behind the male opening bends inward, 

 then turns sharply upon itself, and again bends inward, thus producing a most 

 eflieient mechanism for the retention of sperms in the vagina. The latter opens 

 into the large genital cavity, described below. In the walls of the oviduct lie 

 the shell-glands which are not visible in whole mounts of adult animals, but can 

 be clearly seen in sections. They will be more fully described in the young 

 foi-m in which they are clearly recognisable. 



The testis is a pyriform structure lying close behind the ovary. The vas 

 deferens passes forwards and in the region of the eimis-sae bends upon itself, 

 then ag-ain forwaxd to open into the penis. The vas is a fairly widely dilated 

 tube but no special portion of it can be regarded as a vesicula seminalis. The 

 penis is a rather simple chitinous tube with a distinct curve near its tei-mination. 

 It is lodged within a highly developed cirrus-sac (PI. xiv., fig. 26) which con- 

 sists proximally of a large rounded structure lined with an outer layer of 

 circular muscles, internal to which is a group of radiating muscles, inserted upon 

 tUe beginning of the penis. The sac extends forward and embraces the penis 

 for a considerable distance. Distally it opens by a distinct, heavily chitinised 

 aperture into the great genital cavity (PL xiv., fig. 29). This remarkable 

 stnicture encloses a relatively large space, with collapsed walls, lined by chitin. 

 Into its front portion open the penis and the vagina. The whole is surrounded 

 by a complex musculature. Probably this organ is to be regarded as having an 

 accessory copulatory function. 



On the gills of the same fish which provided the specimens upon which 

 the above description is based there were present other worms, which axe pro- 

 bably the young of this species, since the arrangement of the discal armature, 

 liead-glands, and intestine are identical; but the genital organs are rather simpler 

 than those above described, though they are founded on essentially the same 

 plan (PL xiv., fig. 30). Ovary and testis are well developed, but the former 

 has not yet attained the size it does in the adult worm. The walls of the oviduct 

 lodge a number of small unicellular shellglands, whose ducts pass forward and 

 evidently open . each directly into the ootype. The uterus, which is shai-ply 

 marked off from the latter, is considerably wider and passes straight forwai'd to 

 open close to the male genital aperture. The vagina which is connected with 

 the uterus by a narrow chitinous duet, is constricted anteriorly, then dilated 

 again into a small bulb which gradually tapers off to form a narrow duct open- 

 ing to the exterior. This terminal portion of the organ already has an indication 

 of the twisting which subsequently becomes so evident. The vagina opens into 

 a small crevice, doubtless the rudiment of the remarkable structure that occurs 

 in the adult. The vas deferens is a fairly straight tube, connected distally with 

 a small bulbus ejaeulatorius opening into the penis. The latter is less heavily 

 chitinised than in the adult. The prominent bulbous expansion of the proximal 

 part of the adult cirrus-sac can scarcely be detected in many cases while in 

 others, evidently more advanced individuals, it is more distinct, but not so pro- 

 nounced as in the adult forms. 



Found on the gills of the marine black bream or black fish, G-irella tricuspi- 

 data Q. and Gr. from CaJoundra, South-east Queensland. 



20. L A M E L L o D I s c u s, n.gen. 



Small slender Lepidotreminae in which the body is devoid of scaly papillae. 

 Disc well developed, with the accessory locomotory disc (squamodisc) peculiarly 



