120 



THE CESTOIDEA 



These " phyllidia " are outgrowths of the scolex, and contain a 

 part of the excretory network (Fig. VII. 2) ; they occur under 

 three chief varieties : (a) They retain their simple character with 

 a more or less marked, spoon-shaped depression or " bothridium " 



FIG. XVI. Scolex of various Tetraphyllkfea 



1. Anthobothrium cornucopia, v. Ben., out of Galeus canis (after v. Ben.). The four phyllidia 

 are typically developed, with long stalks, and a simple unarmed and undivided bothridium. 



2. Rhinebothrium flexile, Lint., out of Trygon centrum (after Linton). Each bothridium is 

 divided into numerous loculi by a median, longitudinal, and a series of transverse ridges. 



3. Phyllobothrium thridax, v. Ben., out of Squatina vulgaris (after Zschokke). Each both- 

 . ridium is provided with an accessory sucker (a). 



4. Echeiieibothrium variabile, v. Ben., in various species of Raia (after Linton). In addi- 

 tion to the usual four bothridia here well developed carried by the phyllidia, there is an 

 apical, rostellar sucker (x). 



at the free end ; the point of attachment to the scolex is con- 

 stricted, and this narrow base may be prolonged to form a distinct 

 peduncle, or this simple depression in the Pliyllobothrinae (Fig. 

 XVI. 2) may be subdivided by transverse ridges into a small 

 number of " loculi," as in the posterior sucker of such a Trematode 



