88 Snail-Leeches. 



the water. A brown, semicircular, coriaceous plate is seen about 

 the twelfth ring, its convex side pointing towards the posterior 

 extremity, opening through the integument of body externally; 

 this plate is sometimes rudimentary. Ova attached to the 

 abdominal surface, the centre of which forms a deep cavity by 

 the folding together of the margins ; this is best seen when 

 the animal extends itself in locomotion. Stomachal ceeca six 

 pairs, anterior pair divided upwards. This leech often keeps 

 its posterior part doubled up in a heap, and draws it along in 

 this position. This is the smallest of the Glossiphonidce, and 

 is extremely common. It produces its eggs in April, May, 

 and June ; the young attaching themselves by their posterior 

 suckers to the abdomen. Length about five lines. 



G. tessellata. — The largest and most leech-like of the family. 

 Body, when at rest, oblong, anterior extremity being more 

 rounded than in other species ; colour, dull olive green, with 

 about five rows of light yellow spots arranged longitudinally ; 

 the spots on the margins are much the largest. Body nearly 

 an inch in length ; gelatinous ; posterior sucker large ; oral 

 sucker sub -triangular, forming, when the animal extends itself, 

 a hollow cup-shaped cavity. Eyes, four pair; the first pair 

 slightly converging. Deposits its ova (June and July) on 

 submerged bodies, and sits upon them ; the pellucid vitelline 

 membranes, which are large, may often be found adhering by 

 their pellicles to leaves, stones, etc., after the embryos have 

 left them. The young of this species is very beautiful, being 

 in its earliest stage of a pinkish hue ; but this delicate appear- 

 ance changes to a dull olive, marked with longitudinal lines of 

 white spots. Miiller has very correctly observed that this 

 species is so variable, according to age, that the individuals 

 can only be recognized as belonging to the same species by 

 continual observation. It is the most active of the family, and 

 moves about with great celerity. It is generally considered 

 rare ; but although certainly far from common, I have little 

 doubt that careful searches after this species would be re- 

 warded with success. It is not uncommon in the Shropshire 

 Union Canal, from whence I have obtained several specimens. 

 I have also found it in weedy pools. It is the most prolific 

 of all the family ; as many as 200 young ones may be counted 

 attached to the mother. 



G. marginala. — This is a rare but very pretty little Glossi- 

 phon; it was added by myself to the English fauna in 1860. 

 I give the description of this species as recorded in the 

 Annals and Magazine of Natural History, No. 28, April, 

 1860, p. 249. 



" Body, when at rest, nearly elliptical, but narrowing 

 towards the anterior extremity, capable of great elongation 



