BY T. HARVEY JOHNSTON AND 0. W. TIEGS. 123 



Monticelli (1903) placed Dionchus, Anoplodiseus, Lophocotyle and Merizo- 

 cotyle in the B'lonocotyUdae, Awisocotylinae ; while Pratt (1900) grouped the 

 first, third and fourth of these in his key as a separate section of the Monocoty- 

 lidae, wliile the second was placed among the Gyrodactylidae. 



31. Dionchus Goto, 1899. 



DioncMnae. Goto defined the genus thus: — "Body flat and elongated; with 

 a single posterior sucker, the inner surface of which is divided by radial ridges 

 into ten areas, with one pair of chitinous hooks. Mouth at a short distance from 

 the front end; intestine bifurcated, simple. With four eye-spots. Porus geni- 

 talis communis submarginal. Testes two, one lying in front of the other. No 

 vagina." 



To this diagnosis may be added : — strong development of cephalic glands 

 whose ducts do not become concentrated into head-organs, but open separately 

 round the margin of the head. 



Type and only known species, D. agassizi Goto, 1899, from gills of a 

 marine fish Remora brachyptera. From Newport, Rhode Island, U.S.A. 



Goto regards this form as combining Gyrodaetylid and Monocotylid charac- 

 ters, showing a specially close resemblance to Fridericianella in the former group, 

 a genus which seems to us to be intermediate between Calceostona and Dionchus. 



32. D I o X c n T R E M A, n.gen. 



(Syn. Acanthodiscus MaeCallum, 1916, nee 1918; nee Uhlig, 1906.) 



A small species with the disc distinctly marked off from the body and pro- 

 vided with two large and numerous smaller hooks. Cephalic glands prominent, 

 opening" on the surface by scattered apertures. Eyes present. Intestine 

 bifurcate. Ovary simple. Vagina present. Vitelline system well developed. 

 Two testes. Penis simple. 



Type (and only known) species, D. remorae (MacCaUum, 1916) J. &. T. 



From the gills of Eeheneis naticrates, from New York Aquarium. 



The presence of distinct cephalic glands opening apparently diffusely on 

 the head, two large discal hooks and a pair of testes show that Dionchotrema is 

 closely allied to DioncJius. In the latter genus, however, the vagina is lacking. 



MaeCallum (1916) placed this form in the Family Gyrodactylidae, genus 

 AeantJwdiscus, a name which had not previously been used in connection with 

 Trematoda. Two years later he employed the same name, desig-nating it as a 

 new genus, so presumably he had intended employing it as such in 1916, though 

 it was not so indicated and no generic diagnosis was given. The two species 

 which he referred to this generic name are considered by us to represent two 

 different genera and, since the name was already preoccupied by Uhlig in 1906 

 for a Molluscan genus, we have proposed two new genera viz., Dionehotrema 

 for his A. remorae, and Protomierocotyle for his A. mirabilis (see later). 



Appendix to Dioncliinae. 



33. Anoplodiscus Sonsino, 1890. 



In 1890 Sonsino described a new trematode to which he gave the name 

 Anoplodiseus richiardii, from the gills of a marine fish, Pagrus orphus. He 

 regarded it as having affinities with the Tiistomids and Gyrodactylids. His 

 very insufficient description was slightly amplified in 1905 by Monticelli. From 



