M Turner 137 



No Coenurus has been recorded in either the rat or mouse before, 

 though they have been found in other members of the group Muridae. 

 In the Jerboa is Coenurus polytuberculosus, Megnin, 1880, and in the 

 Gerbille, Coenurus glomeraius, Railliet et Henry, 1915. 



Unfortunately the cysts from the mice are very immature, the buds 

 having not yet developed hooks or suckers so that it is impossible to 

 compare them with other forms of Coenurus. 



Besides these from the members of the Muridae, the group Coenurus 

 contains five more species, viz. C. cerebralis of sheep, C. gaigeri of goats, 

 C. serialis of rabbits, C. ramosus of Macacus sinicus and C. lemuris of 

 lemurs. Of these C. cerebralis and C. serialis most nearly resemble that 

 from the rat. 



Examination of the scolices of the rat Coenurus, of C. serialis, of 

 C. cerebralis and of C. glomeraius has revealed the fact that there is a 

 considerable amount of variation amongst the individual hooks. Hooks 

 from the same scolex vary in length and shape within fairly wide limits, 

 so that it is in some cases difficult to distinguish between two species 

 when the material for diagnosis consists solely of a limited number of 

 hooks. 



Coenurus from the Rat. 



The entire cyst is ellipsoidal in shape and measures about 2 cm. in 

 length by 1 cm. in breadth. The cyst- wall is thin, and transparent enough 

 to allow the buds, which cover almost the whole of the inner surface of 

 the wall, to be clearly seen. About twenty buds project from the outer 

 surface of the cyst. Each head, in both lateral and face view, is approxi- 

 mately circular in shape, with a diameter of about 650 /x. 



The suckers are of fairly large size. Their muscular bulbs have dia- 

 meters of about 230/x.. The rostellum is about 330/x in diameter and bears 

 a double crown of from 24 to 28 hooks. 



The large hooks are from 130/x to 145/i in length and the blade, 

 handle and guard are all well developed. 



The blade is moderately curved. 



The handle is long and straight and very slightly tapering. Its dorsal 

 and ventral margins are practically parallel and somewhat sinuous. A 

 notch is sometimes present on the dorsal margin about the middle of the 

 handle. The free end of the handle turns dorsally. 



A line drawn transversely through the centre of the guard shows that 

 the handle is considerably longer than the blade. This gives the handle 

 a slender appearance. 



Ann. Biol, vi 10 



