W. A. Harping 
149 
breadth. Colour grayish olive above, pale gray beneath ; the anterior 
extremity and the posterior sucker are finely sprinkled with black, 
stellate, superficial pigment cells. 
Dorsal surface with six longitudinal series of rounded yellowish spots. 
The spots composing four of these series occur on the first ring of each 
somite and correspond to the outer paramediau and intermediate sense 
organs, the inner paramarginal sense organs on this ring being without 
spots, whilst the spots composing the two remaining series are situated 
on the outer paramarginal lines on the second ring of each somite. The 
paramarginal spots are the largest and sometimes overlap on to the 
ventral surface. All the spots are subject to individual fluctuations in 
size; usually some of them are imperfectly developed or absent. 
Papillae, generally small and scarcely perceptible, occur dorsally on the 
first rings of each somite and correspond to the outer paramedian, inter¬ 
mediate and inner paramarginal sense organs. Similar papillae are 
situated on the outer paramedian and inner paramarginal lines and 
occasionally (Livanow) on the intermediate lines on the first rings of 
each somite on the ventral surface. These are not associated with 
yellow spots. 
74 rings. Somite I uniannulate, somites II and XXIV—XXVII 
biannulate; the 21 somites III—XXIII are complete with three rings. 
The four pairs of eyes lie respectively on the first rings of somites 
II, III, IV and V, that is, upon rings 2, 4, 7 and 10. 
The male genital orifice lies between rings 28 and 29, that is, 
between the first and second rings of somite XI; the female orifice is 
four rings behind the male, between rings 32 and 33. 
The anus opens behind ring 73 and is separated by the seventy- 
fourth and last ring, which is incomplete, from the posterior sucker. 
Dimensions. The following measurements are taken from the 
single living English example which I have had the opportunity of 
examining. 
At rest, but moderately extended, 16 mm. long and 2 mm. wide. 
At rest, in extreme contraction, about 8 mm. long and 4 mm. wide. In 
extreme extension, 24 mm. long. 
Larger dimensions are probably attained; the results of the following 
observers are however somewhat conflicting:—O. F. Muller, 1774, 18 
lines long and 5 lines wide; Brightwell, 1842 (English example), “about 
an inch long”; Moquin-Tandon, 1846, 18—25 mm. long and 4—5 mm. 
wide; Thompson, 1846 (Irish examples) “size commonly.,,nine lines”; 
Parasitology ur 10 
