208 CBPHALOTHEIX LINEARIS. 



Body. — Six to eight inches or more in length, and about a line in breadth, generally 

 resembling that of Linens lacteus, except in the greater tendency to encircling furrows. 



Colour.— Richly roseate in front, the rest of the body being pale pinkish-yellow or 

 yellowish-white. 



Head. — Spathulate, as in the above-mentioned species, the lateral fissures, of course, being 

 absent. The eyes are also fewer in number and smaller, but similarly arranged. The 

 mouth is large and situated far backwards, the position and size being equally interesting in 

 this group. 



So like was this species to Linens lacteus (Plate V, fig. 3), that most examples were 

 consigned to spirit before a more critical examination discovered the essential differences. Those 

 specimens; even, which were destined for transmission southward proved so delicate as to break 

 into short fragments in a day or two. The structure of the body-wall and the proboscis at once 

 distinguishes it from the Lineidce, while the fact that the nerves in the longitudinal muscular coat 

 do not quite reach its outer border separates it from its ally Carinella linearis. 



Family IV. — Cephalothricimi. 

 Genus XII. — Cephalothrix, 1 (Ersted, 1844. 



This genus was established by A. S. (Ersted in his ' Entwurf Plattwurmer' for the reception of 

 animals identical with the Planaria linearis of Jens Rathke. The typical form was distinguished 

 by several names, and a variety included also under the genus Astemma of the same author, 

 for I consider the distinctions as to the presence or absence of eye-specks and the vague remarks 

 about respiratory fissures of little consequence. 



Generic character. — Head cylindrical, slightly tapered in front ; eyeless, or with a few 

 obscure pigment-specks. Cephalic fissures and sacs absent. Mouth situated a considerable 

 distance behind the snout. 



Cephalothrix linearis, Jens Bathke. Plate IV, figs. 4 and 5. 



Specific character. — Body extremely attenuated, pale yellowish or skin-colour ; often with 

 reddish grains towards the tip of the snout. 



Synonyms. 

 1799. Planaria linearis, Jens Rathke. Skrivter af Naturhist. Selsk., v, p. 84, tab. 3, f. 11. 

 1829. „ filiformiSj Johnston. Zool. Jour., vol. iv, p. 56. 



1837. Nemertes (Borlasia) rufifrons, Johnston. Mag. Zool. and Bot., vol. i, p. 538, pi. 18, f. 4 and 5. 

 1844. Cephalothrix bioculata, (Ersted. Entw. Plattw., p. 81, woodcut 12. 



„ „ caeca, Ibid. Op. cit., p. 81, tab. 3, f. 39. 



„ „ linearis, Ibid. Op. cit., p. 82 (note under C. caeca) . 



1 KrfaXrj, the head, and SpiZ a hair. There is a genus of Lamellicorn beetles (established by Hope 

 in 1837) called Cephalotrichia. 



