638 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 40. 



33U 



Fig. 1. 



-SrllVEONCOTJLNIA UNCINATA. 



Natural size. 



Entire worm. 



cm. from the posterior end 

 (alcoholic material). Segments 

 several hundred in number, 

 broader than long except at 

 the posterior end of the strobila 

 where they may be slightly 

 longer than broad. (Fig. 4.) 

 Head (fig. 2), 400 to 450 ;x 

 broad by 280 to 300 n long. 

 Suckers unarmed, 175 to 200/t 

 in diameter. Rostellum sim- 

 ple, truncate conical in shape, 

 150 to 175 p long by 190 to 

 200 p. broad at its base, armed 

 with numerous hammer-shaped 

 hooks (fig. 3), 25 to 30 p long, 

 arranged in 10 to 12 rows. Re- 

 tracted rostellum lies within 

 a cavity whose inner surface 

 is lined with an armature of 

 very numerous short spines, 

 which evidently form a spiny 

 zone back of the rostellum 

 when the latter is protracted. 

 Unsegmented neck region prac- 

 tically nil. Just back of the 

 head the breadth of the strobila 

 is slightly less than that of the 

 head, varying with the state of 

 contraction. Posterior bor- 

 ders of each segment, except 

 in the posterior region of the 

 strobila, overlap the succeed- 

 ing segment nearly half way. 

 Genital pores unilateral. (Fig. 

 4, g. p.) The genital pore in 

 younger segments is located in 

 the lateral margin just poste- 

 rior of the edge of the pos- 

 terior border of the preceding 

 segment. In gravid segments 

 (fig. 4) the posterior borders 

 overlap the succeeding seg- 

 ments but slightly, and the 

 genital pore is located a short 



