SEA-FISHERIES LABORATORY. 105 
Monocotylidae. Taschenberg’s diagnosis of this group 
(which I quote from Braun) includes the following 
characters :—Anterior accessory suckers absent; posterior 
sucker small, or normally developed, and with chitinous 
hooks; genital opening median; vaginae double and 
paired. But Gotto has described a species of Monocotyle 
(JZ. 172mae) in which the vagina is single and unpaired, 
and there are probably other species which present the 
same character, and all the forms described may not have 
been investigated in sufficient detail to make it certain 
that the vagina is really double. Of the genera of 
Monocotylidae only Pseudocotyle has a posterior sucker 
entirely devoid of radial ridges and hooks, while these 
are present in both Callicotyle and Monocotyle. The 
worm here described, therefore, approximates to the 
former, and diverges from the latter genera, so far as the 
characters of the posterior suckers are concerned. 
But Pseudocotyle differs in that it possesses numerous 
testes, and has an intestine with numerous lateral 
branches on the rami. The original diagnosis given by 
van Beneden and Hesse says:—‘‘ Point de ventouses a 
coté de la bouche, et la ventouse postérieure du corps tres 
variable dans sa forme comme dans la grandeur; cette 
ventouse ne renferme ni rayons ni crochets; le canal 
intestinal est ramifé ”’ 
Now the branching of the intes- 
tine and the presence of numerous testes certainly 
constitute a fundamental difference between Pseudocotyle 
and the form now being described. It is conceivable that 
such a superficial character as the presence or absence of 
the rays and hooks in the posterior may not be a character 
of very great taxonomic value. If it is not, then we may 
identify the Port Erin worm with the genus Monocotyle. 
In Monocotyle the intestine is simple, consisting of 
two lateral vessels, devoid of diverticula of any kind. The 
H 
