136 
The British Leeches 
somite. Or the colour may be of a roseate hue which fades in alcohol. 
(R. Blanchard.) 
Somites XIY—XXIV in the posterior region of the body are 
complete with three rings. Each of the 33 rings composing these 
eleven somites carries a pair of lateral, foliaceous, crispate branchiae. 
A pulsating vesicle is situated at the base of each of the branchiae 
arising from the first ring of each somite. Six eyes, disposed in a 
transverse curved line, on the dorsal surface of the anterior sucker, 
in somite V (Apathy). The male genital orifice is situated between 
the two rings of somite XI; the female orifice lies upon the first ring 
of somite XII; somites X, XI and XII, each composed of two rings, 
form the clitellum. The anus lies between somites XXV and XXVI. 
Length 30—50 mm.; width 8—16 mm. including the branchiae. 
[The following measurements are taken from an example in alcohol, 
from Naples, in the possession of the University Museum of Zoology, 
Cambridge:—Length 49 mm., width of body 11 mm., total width 
including branchiae 16 mm.; diameter of anterior sucker 35 mm., of 
posterior sucker 9 mm.] 
Distribution, Hosts. B. torpedinis is parasitic chiefly upon the 
electric rays {Torpedo). Blanchard records it from a wrasse ( Labrus sp.) 
and from Rhinobatus thouin ; van Beneden and Hesse found it on a 
turbot ( Psettci [ Rhombus ] maxima) and its occurrence on Raia clavata 
is noted below. It is found in the Mediterranean, and in the Atlantic 
where its range extends along the West coast of Africa as far as 
Senegal (Blanchard). In British waters it has been recorded twice. 
(1) Johnston (1865, p. 39) catalogues an English example (precise locality 
unknown) taken “ with soles,” and (2) Holt (1899, p. 4) records a single 
individual taken from the pelvic fin of a thornback {Raia clavata) in 
Blacksod Bay on the west coast of Ireland. 
Genus: Trachelobdella, Diesing, 1850. 
Synonymy: 
Calliobdella, van Beneden and Hesse, 1864. Callobdella , R. Blanchard, 1894. 
Ectoparasitic on marine fish. Without eyes. Anterior sucker reduced. 
Posterior region of the body cylindrical or flattened in young individuals, 
ventricose in adults, with paired lateral pulsating vesicles. Complete 
somite composed of six rings, formed by the more or less distinct sub¬ 
division of three primitive rings. 
