86 NEW GYRODACTYLOID TBEMATODES FROM AUSTRALIAN PISHES, 



TEEMATODA HETEROCOTYLEA. 



Siiperfamily G Y B D A C T Y L I D E A, n. superfam. 



Tliis superfamily includes certaia monogenetic trematodes characterised by 

 the absence of suckere of the ordinary type, although the higher and more 

 specialised members of the group may have structures which function as such. 



The organ of attachment to its host is a posterior clasping disc which, 

 may or may not be distinctly mai-ked off from the body of the worm. The 

 disc is supplied with a hook apparatus which may reach an extraordinary degi'ee 

 of complexity. 



At the anterior end of the parasite (except in the Monoootylidae) are 

 masses of glandular tissue, which open on the surface by very charactferistic 

 "head organs," or, in the higher members of the superfamily, by a very large 

 number of minute ducts, not concentrated in groups. In the Monocotylidae these 

 glands have apparently disappeared. 



The mouth leads into a buccal cavity which may be short or fairly long; 

 never very long. A pharynx is always present. An oesophagus may be present 

 or absent. The intestine has one or two limbs, with or without caeca. 



Excretory ducts open either at the anterior end or, in some forms, probably 

 at the posterior end. 



Eyes may be present or absent. The nervous system consists of a poorly 

 developed brain, below or considerably behind the eyes. A pair of lateral nerves, 

 from which smaller branches arise, are given off from the brain. 



The testis is a compact or only slightly lobed organ, single or double, and 

 never lies anterior to the ovary. The vas deferens may be a simple tube hardly 

 expanded into a vesicula seminalis, or it may be widely dilated, sometimes 

 enormously so in the Australian species. A bulbus ejaculatorius may or may 

 not be present. The ciiTus may range from a simple chitinous tube to a struc- 

 ture of considerable complexity, wbile an accessory clasping apparatus may 

 occur. 



The ovary may be a branched or unbranched organ, lying either in the 

 midline or asymmetrically. A vagina may be present (single or double) or 

 absent, and there may be a receptaculum seminis connected with it. 



Shell-glands may vary from simple glandular thickenings of the ootype, to 

 very prominent glands connected by long ducts with the female duct. The 

 female aperture usually lies immediately behind the male opening, but some- 

 times at a considerable distance from it, generally laterally. Never more than 

 one egg is present in the uterus. The egg may be laid, or it may be retained 

 in the uteras to develop into a young worm which may, while in utero, produce a 

 second generation. 



The yolk system may be poorly or strongly developed. In the most piimitive 

 members of the group there is a very distinct communication between the yolk 

 system and the intestine in the posterior region of the animal. 



The members of the group occur, as far as is known, on the gills, nasal 

 gland, or skin of fishes, both Teleosts and Elasmobranchs. 



A>// to families of G;\Todaetyloidea. 



A, a. Glandular structures present on head .. B. 



b. Glandular structures entirely absent Monocotylidae 



B. a. Ducts from the glands concentrated into distinct "head-organs" C. 



b. Ducts from glands scattered diffusely over part ofl the head . Caloeostomidae 



