Mr. R. Templeton on Aulastoma heluo. 137 
X VI.— Observations on Aulastoma heluo. 
By Rosert Tempweton, Esq. 
[Plate VIII. | 
THE leech I am about to describe (Aulastoma heluo) is the 
common horse-leech of the north of Ireland, and may pro- 
bably be more widely distributed. It may be collected in 
sufficient abundance two miles south of Belfast, on the moist 
banks of drains and wet ditches communicating with the river 
Blackwater between Stockman’s Lane and the meadows in 
rear of the industrial school. It is found under stones, clumps 
of very coarse tangled grass or weedy masses, during the 
summer months; it seldom remains long in the water or 
pools of the ditches; when swimming it becomes lengthened 
out and very flat, It is gluttonously voracious, greedily 
gorging itself with earthworms, aquatic larve, small stickle- 
backs, and various thin-shelled Helices, Planorbes, Limnee, 
&c. In size it reaches to 23 inches in length; the body is 
widest behind (4 inch nearly), the margin curvilinear; thence 
it narrows gradually to the head, which is small (5 inch); 
the sides of the body are rounded, the dorsum slightly con- 
vex, its colour very dark olive-green, almost greenish black, 
the belly greyish ash-colour. There are lighter-coloured 
specimens, which have a tinge of brown or yellow; but these 
are exceptional. Selecting a model specimen, the colour 
appears tolerably uniform, a little lighter and brighter down 
the middle line of the back, and the rings, of which there are 
ninety-five quite distinct, are readily made out. The sexual 
organs are between the twenty-fifth and twenty-sixth rings 
and the twenty-ninth and thirtieth rings. Let a small piece 
of plate-glass be now placed on the back, so that the entire 
surface may lose the rounded form given to it by the rings, 
become quite flat, and no longer glisten, a very handsome 
arrangement of longitudinal lines is exhibited; these lines, 
four in number on each side of the middle of the back, have 
avery patchy look, are very dark, but usually a little less 
deeply tinted in the middle, so that each of the lines often 
looks distinctly double; they are interrupted at the passage 
from ring to rmg. ‘The innermost of these sets of four lines, 
enclosing a moderately narrow space running the entire length 
of the back, and of rather brighter hue than the rest of the 
dorsum, may be subdivided into nineteen definite lengths of 
five rings, with the same configuration over and over again 
repeated from head to tail. Within these five rings the first 
Ann. & Mag. N. Hist. Ser. 5. Vol. viii. 10 
