STUDIES ON THE DIGENETIC TREMA'TODES. 453 
widely distributed, it having now been recorded from 
thirteen different hosts in this country. 
On the classification of the ALLOCREADIINA. 
We are now in a position to recognise, at least, four well- 
defined groups of the ALLOCREADIINm, namely, the genera 
Allocreadium lss., sens strict.. Helicometra Odhn., 
Podocotyle (Duj.) Odhn. and Lebouria Mihi. The types of 
other groups have been indicated by Odhner,' and he has 
also constructed a key for the diagnosis of several species.’ 
In all probability the ultimate division of the sub-family will 
proceed along the lines he has laid down, with certain 
modifications. The imperfect knowledge which we as yet 
possess of the internal structure of many of these forms renders 
premature any attempt at a complete classification of the 
sub-family, and we must be content for the present with 
speculations. On the other hand, it is advisable in the 
interests of systematic work, that as many forms as are 
sufficiently well known should be assigned their true generic 
place, and on that account I venture to propose, as the types 
of two new genera, two species which have already been 
considered by Odhner as probable generic types, and of 
which I have personal knowledge,*? namely, Distomum 
labracis Dujardin and Dist. genu Rud. Both species 
have been re-described by Odhner,* and the first also by 
Johnstone.’ I propose Dist. labracis Duj. as the type of 
the new genus Cainocreadium with the following pro- 
visional definition : 
Large ALLocrEapIIN® with extended, flattened body. 
*“Die Trematoden des arktischen Gebietes”; in ‘Fauna Arctica,’ 
lv, p. 327. 
* “Revision einig. Arten der Gattung Allocreadiine,” in ‘Zool. 
Jahrb.,’ syst. xiv, p. 516. 
* Thanks in the first instance to my friend Mr. Johnstone, who sent 
me his specimens of Allocreadium labracis Duj. 
* * Zool. Jahrb.,’ syst. xiv, pp. 496-499 and 514-515, pl. xxxiii, figs. 3 
and 11. 
* ‘Trans. Biological Soc.,’ Liverpool, xxii (1908), pp. 44-53, pl. iii. 
