106 NEW GYRODACTTLOID TREMATODES FROM AUSTRALIAN PISHES, 



Flabellodiscus simplex, n.sp. (Plate xviii., fig's. 54-55; xix., figs. 61, 62.) 



Length .53 mm., breadth .1 mm. The disc is broader than the body, measur- 

 ing .112 mm. across. 



In external appearance this parasite closely resembles Lepidotrema, even in 

 regard to the arrangement of the discal armature. The disposition of the minor 

 hooks is shown in PI. xix., fig. 61. One pair of hooks is present between the 

 cross-bars, as is the case also in Lepidotrema fuliginosum. The ventral trans- 

 verse cross-bar differs slightly from that generally found in the last-named genus 

 in being slightly angular, the edge opposite the obtuse angle giving off the 

 small supporting ehitin-piece. 



The scale-like papillae of the epidermis are absent on the dorsal surface 

 (PI. xix., fig. 62). No further details of the stracture of the body walls could 

 be seen distinctly. 



The alimentary canal and its associated glands are similar to those of 

 Lepidotnema, the blindly-ending intestine being in both cases devoid of caeca. 



In one specimen examined part of the nervous system could be seen. The 

 brain lies between the eyes, immediately anterior to the pharynx, the lateral 

 nerve cords curving round part of the pharynx and pa.ssing down the sides of 

 the worm, close to the alimentary canal. Immediately behind the eyes two pairs 

 of nerves are given off, one running upward to the head, the second inward 

 towards the pharynx. Several other branches arise from the lateral nerve- 

 trunks, both on their inner and outer sides (PI. xviii., fig. 55). The nerve-trunks 

 in the posterior region of the worm could not be recognised. No trace of 

 excretory system could be detected. 



It is in the structure of the reproductive system (PI. xviii., fig. 54) that 

 the wol-m differs so' much from Lepidotrema. 



The testis is a curious uniform stnicture, situated above the anterior end 

 of the ovary. The vas deferens is a long, very narrow, convoluted tube which 

 opens into a highly dilated vesicula lying transversely across the body, im- 

 mediately in front of the ovary, while the remainder of the sperm duct is a 

 short slightly convoluted tube, which leads into the cirrus. The base of the 

 latter is imbedded in a great mass of muscle. The cirrus is a much simpler 

 structure, the twisted chitinous flange present in Lepidotrema being quite absent. 

 It opens in the mid-ventral region of the animal a short distance behind the 

 pharynx. Connected with its termination is a minute unicellular prostate gland. 



The anterior end of the ovary is bent sharply upon itself and it is from 

 this region, and not from the median portion of the gland, that the female 

 duets arise. The oviduct, which is visible only with gi'eat difficulty, is a rather 

 wide tube running forward to a point a little behind the end of the cirrus. 

 It is embedded in a dense parenchyma of a rather fibrous nature, in which lie 

 a number of large pyriform -cells, heavily staining, and evidently to be regarded 

 as shell glands, but their ducts could not be seen. The vagina is remarkable 

 in that it does not ran outwards along the ventral body wall as in other species 

 of the genus Lepidotrema, but lies immediately below the dorsal body wall em- 

 bedded, in part, in the dense parenchyma which surrounds the oviduct. It is a 

 much narrower tube than is found in that genus. Shortly after leaving the 

 oviduct it dilates, and this dilatation is seen to contain a kind of granular material, 

 giving it a resemblance to a prostate gland. This portion may be regarded as 

 a receptaculum seminis, filled with sperms. The tube there naiTows, passes for- 

 ward to a point immediately in front of the opening of the oviduct, then turns 

 sharply upon itself, travels backward, downward, and finally forward again 



