92 NEW GYBODACTYLOID TEEMATdDES FROM AUSTRALIAN FISHES, 



The following species appear to belong to Ba-ctylogyrus : — D. parvus Wege- 

 nef, 1910; t). difformk Wag., 1857; B. fraternus Wegener, 1910; D. minor Wag., 

 1857; D. crucifer Wag., 1857; D. cornu Litist., 1878; D. intermedins Wegener, 

 1910; D. falcdtus (WedL, 1857) Dies., 1858; D. alatus Linst., 1878; D. sphyrna 

 Linstow, 1878; D. sinvilis Wegener, 1910; D. fallax Wag., 1857; D. macracanthiis 

 Wegener, 1910; D. amphibothrium Wag., 1857; D. anchoratus (Duj., 1845) Wag., 

 1857; ? D. forceps Leuckart, 1857; D. gracilis Wiedl., 1861; D. major Wag., 1857; 

 D. malleus Linstow, 1877; D. megastoma Wag., 1857; B. m.ollis (WedL, 1857) 

 Dies., 1858; B. siluri Wag., 1857; B. tenuis (Wedl., 1857) Dies., 1858; B. 

 trigonostoma Wag., 1857; B. tuba Linst., 1878; B. inversus Goto and Kikuchi, 

 1917 (Japan); B. d/wjardinianus Dies., 1850; Z>. auriculatus (Nordm., 1832), 

 Dies., 1850; B. wncinatiis Wag., 1857. 



Subfamily II. TETRAONCHINAE Monticelli, 1903.— emend. J. &. T. 

 (Syn. Biplectaninae Monticelli, 1903; Amphibdellidae Carus, 1885.) 



Gyrodactylidae with the cuticle devoid of scaly papillae. The disc either 

 sharply constricted off from the body, or merging into it directly. Four large 

 hooks always present. Eyes present or absent. The intestine either a single 

 median tube, or bifurcated, with the limbs ending blindly or joining up behind. 

 Intestinal caeca present or absent. 



Testis occasionally, ovajt-y never, lobed. Vagina present or absent. Penis 

 generally simple, occasionally somewhat complex, but never attaining the, extra- 

 ordinary degree of complexity seen in the next subfamily (Lepidotreminae). 

 Occasionally an accessory male copulatoi-y stmcture present. 



From the gills of marine and freshwater fishes. 



This subfamily includes the following genera and subgenera: — Anchylodiscus, 

 n.gen.; Ancyrocephalus Creplin, 1839; Bactylodiscus Olsson, 1893; Biplectaiio- 

 trema, n.gen.; Tetraonclius Diesing, 1858 (type, genus) ; Amphibdella Chatin, 1874; 

 Haliotrema, n.gen.; Baitreosoma, n.gen.; Empleurosoma, n.gen.; Tetrancistrum 

 Goto and Kikuchi, 1917. 



Key to genera of Tetraonchinae. 



A. 1. Body very distinctly constricted near mid-region B. 



2. Body not constricted C. 



B. 1. Testis and ovary in posterior region of body: eyes absent; intestinal limibs 



not connected behind Haliotrema. 



2. Testis and ovary near middle of body: eyes present; intestinal limbs con- 

 nected behind Baitreosoma. 



C. 1. Intestine bifurcated D. 



2. Intestine not bifurcated Tetraonchus. 



D. 1. Intestinal limbs provided with caeca Tetrancistrum. 



2. Intestinal limbs devoid of caeca E. 



E. 1. Disc connected with body by a distinct petiole, and developed laterally into 



short processes Bactylodiscus. 



2. Otherwise "■ ■ ■ ■ ■ P. 



P. 1. Body rather long and slender; intestinal limbs ending blindly G. 



2. Body robust; intestinal limbs connected behind .. Empleurosoma. 



G. 1, Yolk system confined to a region behind the transverse yolk-duct 



Amphibdella. 



2. Yolk system extending as far as, or almost as far aSj the pharynx H. 



H. 1. Yolk system consisting of a longitudinal row of separate yolk-glands. 



Biplectan o trsma. 



2. Yolk system continuous on each side I. 



I. 1. Vagina absent Anchylodiscus. 



2. Vagina present Ancyrocephalus. 



