BY T. HARVEY JOHNSTON AND O. W. TIEGS. iU/ 



along the ventral body Avail where it opens in the midline. This curious 

 arrangement possibly serves to act like a valve, preventing the spei-ms from 

 leaving the vagina. 



The vitellaria of the fully-grown worm are strongly developed and are in 

 general an'angement similar to those of Lepidotnema. In the young forms yolk 

 itself is present only to a small extent. 



The egg measures .05 mm. by .044 mm. It is rather more rounded than in 

 Lepid-otrema and the spine is absent. 



In young specimens the reproductive system is of the same type, the vesicuJa 

 seminalis appearing as a narrow transverse tube immediately in front of the 

 ovary. The cirrus is much simpler than in the adult (PI. six., fig. 61). 



Found on the gills of Therapon fuliginosus Macleay, from the Thomson 

 Biver, at Longreach, Central Queensland. 



17. L E p I D T B s, n.gen. 



Lepidotreminae. In this genus the scale-like body papillae ai-e confined to 

 the posterior half of the worm and the squamodisc is devoid of hooks. The pos- 

 terior disc has four large hooks, supported by intennediate chitinous bars, as 

 well as six pairs of smaller peripheral hooks. 



Four paii-s of head-organs axe present. The intestine ends blindly and is 

 devoid of caeca. Four eyes. Penis simple. Vagina simple, opening laterally; 

 receptaeulum seminis present. 



Found, so far, only on the gills of a freshwater fish, the golden perch or 

 yeUow-belly, Plectroplites ambiguus Richardson. 



Type species, L. fluviatilis J. & T. 



Lepidotes flttviatilis, n.sp. (Plate sx., figs. 65-72; xxi., flg. 73.) 



This is a rather large species, measuring .95 mm. in length, and .26 rom. in 

 greatest breadth. In preserved specimens the gi'eyish colour of the parasite 

 contrasts sharply with the creamy-yellow of the gill filament. 



The shape of the worm varies considerably according to the state of con- 

 traction, being sometimes long and slender, at other times much shorter and rather 

 thick-set. The disc (PI. xx., fig. 67) is very prominent and the arrangement 

 of the hook apparatus complex. Four large hooks are present, the dorsal pair 

 long and slender, the ventral shorter and possessing a, biramous basal portion. 

 Muscles can be seen inserted into the base of the hooks. 



As in Lepidotrema there is a complex chitinous supporting apparatus which 

 does not, however, articulate with the hooks, but seems rather to strengthen the 

 disc. It consists of three bars, a central one with two ventrally and outwardly 

 directed projections, and two lateral outwardly directed pieces closely articulated 

 with the latter. Only six pairs of minute peripheral hooks could be detected. 



The two scaly sucker-like discs are very prominent, but are entirely devoid 

 of the fan-like hook-armattirfe so characteristic of Lepidotrema. Twenty-five rows 

 of scales are present on each disc (PI. xx., flg. 69). 



The chitinous cuticle is modified on the posterior half of the body to form 

 numea-ous forwardly projecting papillae which are not so densely arranged as in 

 Lepidotrema. Longitudinal and circular musele-layei-s are recognisable. The 

 body-pai-enchyma of the posterior half of the animal is of an extremely loose 

 texture, giving this tissue a reticulate appearance. 



The mouth lies ventrally. immediately in 'front of the pharynx. The latter 

 is large and rounded in dorsal view, and bears numerous unicellular glands in its 



