BRITISH MARINE TURBELLARIA. 245 



This variable species may be easily mistaken for Stylostomum 

 variabile. It is, however, recognisable by the presence of a continuous 

 median gut-branch over the pharynx, whereas in Stylostomum the 

 pharyngeal region appears as an uninterrupted white area, bordered 

 laterally by the gut-diverticula. 



Genus 32. — Eurylepta, Ehrenberg, 1831 (10). 



Body smooth. Tentacles long, tapering. Usually five pairs of secondary 

 gut-diverticula. The intestine is brightly coloured. Male genital 

 pore beneath the hinder end of the pharyngeal sheath. One pair of 

 xiterine glands is present. Cephalic group of eyes extending 

 posteriorly far beyond the brain. 



68. Eurylepta cornuta (0. F. Miiller). 



1776. Planaria cornuta, 0. F. Midler (3). 



1831. Eurylepta cornuta, Ehrenberg (10). 



1832. Planaria CORNUTA, Johnston (11). 

 1845. „ „ Thompson (19). 

 1845. „ „ Johnston (20). 

 1853. „ „ Daly ell (29). 

 1865. Eurylepta cornuta, Johnston (38). 



1865. „ Dalyelli, Johnston (38). 



1866. „ CORNUTA, Ray Lankester (39). 



Length 1*5 — 3*75 cm. Breadth about half the length. Body 

 elliptical during motion, almost circular at rest, broadly rounded 

 behind. In front are two elongate tentacles. The somewhat convex 

 dorsal surface is, with the exception of the margins, opaque, of a bright 

 orange-red colour dotted with white, due to parenchymatous pigment, 

 and to a greater extent to the contents of the alimentary canal. In 

 front an elongated, oval, raised, white ridge represents the underlying 

 pharynx. The ventral surface is of a pale reddish colour, and upon 

 it the gut, male and female apertures, and sucker are visible. The 

 mouth is one-third of the distance from the anterior end to the sucker, 

 i.e., close behind the brain. The pharynx is well developed, cylindrical, 

 extending almost as far back as the centre, in front of which it opens 

 into the extensive main-gut. From this a median and 5 — 6 lateral 

 pairs of branches arise, which after branching slightly end in marginal 

 forked cseca. The minutely moniliform appearance of these is due to 

 the presence of sphincter-muscles at the points of constriction. Each 



