Volume VIII 
JUNE, 1015 
No. 1 
GANYMEDES CRATERE N.G. ET S. 
By W. HAROLD LEIGH-SHARPE, B.Sc., A.C.P., 
Demonstrator in Biology at Guy's Hospital Medical School, London. 
(With 6 Text-figures.) 
My interest having been aroused in Calliohdella lophiA, I requested 
all my friends engaged upon the sea to keep a look-out for any leeches 
that might come to hand and especially for Calliohdella. Accordingly 
on 6. VIII. 1914 I received a specimen of a leech, taken near St Margaret’s 
Hope towards the north-east of S. Ronaldsay in the Isles of Orkney, 
which as far as I can discover has never been described before, and which 
presents peculiar and interesting features not wholly dissimilar from 
those of Calliohdella. I propose to name the leech Ganymedes (or, if 
this name should be pre-occupied, Ganymedehdella) cratere. 
The leech reached me in a moribund condition, and died shortly 
afterwards, it having been captured towards the end of July, and its 
despatch to me having been hindered owing to the outbreak of the war. 
Habitat. This marine leech, a member of the Rhynchobdellidae, or 
jawless leeches, and belonging to the family Ichthyobdelhdae, was 
parasitic upon a fish “with a pronounced anal papilla.” After some 
written discussion with the collector, I have, after careful consideration, 
decided that this fish was an immature male specimen of Callionymus 
lyra about 12 cm. long, some doubt having at first arisen because it is 
the uro-genital and not anal papilla that is so pronounced in Callionymus. 
Assuming that the collector did not mistake the apertures of the fish 
I am now of the opinion that the anal papilla was an artefact produced 
by the adhesion round the anus of the host of the leech’s anterior 
sucker which is furnished with a most powerful muscular rim for the 
1 Leigh-Sharpe (1914), Calliohdella lophii. Parasitology, vn. 204, also (1913), Calliohdella 
lophii, Journ. Mar. Biol. Assoc, x. 81. 
Parasitology vni 
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