248 Rev. W. Houghton on the Snail-Leech. 



XXVII. On the Discovery of the Snail-Leech, Glossiphonia mar- 

 ginata, in England. By the Rev. W. HOUGHTON, M.A., F.L.S. 



[With a Plate.] 



To the Editors of the Annals of Natural History. 

 GENTLEMEN, 



I have to record the occurrence of a species of Glossiphonia 

 (Rawlins Johnson), viz. G. marginata, as an addition to our 

 English fauna. This species has never before been found in any 

 locality in England ; under the name of Hirudo flava, however, 

 Sir J. Daly ell seems to have met with it in Scotland (vide 

 1 Power of the Creator Displayed/ vol. ii. pi. 5. figs. 119). His 

 figures are not at all good ; the characteristic form of the head, 

 however, is sufficiently shown, which is described as being 

 "lanceolate or trout-shaped." The description of Hirudo flava 

 by Dalyell agrees with the characters of Glossiphonia marginata, 

 with the exception of the number of eyes which his specimen 

 possessed. Hirudo flava has only two eyes, whereas Glossiphonia 

 marginata has four; but this discrepancy is easily accounted for 

 when we remember that the number of eyes is not, in this 

 family, by any means constant in all the individuals of any one 

 species. Sometimes the anterior pair are very rudimentary, 

 sometimes entirely absent. Moreover, in G. marginata the 

 anterior pair are considerably smaller than the posterior pair, 

 and might possibly be overlooked. Dalyell's description and 

 drawings were made from specimens which he found during 

 the time of their having either eggs or young adhering to the 

 belly ; and at this time G. marginata is, on the under side, of a 

 bright yellow colour, as are also the ova. The specific name, 

 however, of flava would give a very erroneous notion of the usual 

 colour of this animal, though the name is appropriate enough 

 during the breeding-season. However, I feel pretty certain that 

 Hirudo flava, in spite of these discrepancies, is identical with 

 G. marginata, and has therefore been discovered in Scotland; 

 but I can find no record of its ever having been found in Eng- 

 land. The first specimen of the species I ever saw was found 

 by me in Bala Lake, on the 22nd of June last ; it was attached 

 (more Glossiphoniarum) to the under surface of a stone near the 

 margin of the lake, with a number of yellow eggs underneath it. 

 The only other locality in which I have found G. marginata is 

 in a small stream in Warwickshire, on the Solihull and Barston 

 road, on the right-hand side of the wooden foot-bridge about a 

 mile from the latter village. Here, in the autumn of last year, 

 I found some four or five specimens : the animal is, however, 

 very rare. I have for the last two years confined my attention 

 chiefly to the Glossiphons, and have searched many ponds for 



