246 
Trematodes from Fish 
group appear to be well founded.' It is particularly iu regard to the 
terminal part of the male organs that the finer distinctions have arisen, 
but it seems inadvisable to allow the consideration of these to outweigh 
the value of other structural features. The various modifications of the 
cirrus pouch which are met with in the true Hemiurids appear again 
in the Derogenes group, and if the same narrow limits of classification 
w'ere adopted in this group the necessity would arise of creating a 
number of small sub-families and of erecting the Syncoeliinae into a 
separate family. I am on that account in agreement with Odhner in 
considering that, for the present at any rate, such a scheme of sub¬ 
division would not be advantageous. 
Obviously the two genera, Hemvpera and Derogenoides, must be 
included in the sub-family Syncoeliinae, Derogenoides in close relation 
to Derogenes and Hemipera to Liocerca. In the event of further 
sub-division eventually becoming necessary it is apparent that these two 
pairs would form the nuclei of smaller groups, both differing from the 
true Syncoeliid type in having the ends of the intestines free, and the 
Liocerca-Hemipera group being further distinguished by the inverted 
position of the ovary and testes. 
The inclusion of these two forms within the family Hemiuridae, 
sensu lat, involves slight modifications of Odhner’s amended definition, 
namely : Pars prostatica usually free but not in Hemipera. Ova O'OIS- 
O'lOO mm., usually oval, but sharply pointed at one end in Derogenoides, 
and filamented in Hemipera. 
EEFERENCES. 
Looss, A. (1907). Beitrage zur Systematik der Distomen. Zur Kenntnis der 
Familie Hemiuridae. Zool. Jahrhiich. Aht. f. Syst. xxvi, 63-180. 
Luhe, M. (1901). Ueber Hemiiu’iden. Zool. Anz. xxiv, 473-488. 
Odhner, T. (1904). Die Trematoden des arktiscben Gebietes. Fauna arctica, 
IV (2), 291-372. 
- (1911). Zum natiirlichen System der digenen Trematoden. IV. Zool. Anz. 
XXXVIII, 513-531. 
EXPLANATION OF PLATE XI. 
Fig. 1. Podocotyle syngnathi. Ventral view, x 20. 
Fig. 2. Podocotyle syngnathi. Cirrus pouch and vagina, x 80. 
Fig. 3. Lepidauchcn stenostoma. Ventral view, x 30. 
Fig. 4. Hemipera ovocaudata. Ventral view, x 66. 
Fig. 5. Hemipera ovocaudata. Shell gland complex, x 130. Semi-diagrammatic. 
Fig. 6. Derogenoides ovacutus. Ventral view, x 150. 
