THE CESTOIDEA 119 



slightly, cupped, their margins being extremely mobile and active. The 

 phyllidia may be pedunculated, their depressions (" bothridia ") may be 

 subdivided by ridges into loculi, and in a few cases carry booklets. 

 The copulatory pore is usually marginal; the vagina is anterior to 

 the penis. The proglottids are detached singly, even before the genital 

 organs are fully developed. 



The members of this order are found almost exclusively in the spiral 

 intestine of Selachians (see v. Beneden, 2). 



FAMILY 1. TETRABOTHRIDAE (Tetraphyllidea, v. Ben.) The phyllidia 

 are distinctly constricted at the base. SUB-FAMILY 1. TETRABOTHRINAE. 

 Phyllidia simple and attached by a broad base. Phyllobothrium, v. 

 Ben. (Fig. XVI. 3) ; Tetrabothrium, Olss. ; Calyptrobothrium, Montic. ; 

 Monorygma, Dies. ; Ceratobothrium, Montic. ; Orygmatobothrium, Dies. ; 

 Marsipocephalus, Wedl. ; M. rectangulus, Wedl., in Heterobranchus 

 anguillaris of the Nile ; Prosthecocotyle, Montic. ; P. forsteri, in dolphin ; 

 Dinobothrium, v. Ben. ; Diplobothrium, v. Ben. ; Zygobothrium, Dies. ; 

 Pelichnibothrium, Montic, ; Peltidocotyle, Dies., scolex globular, dilated, 

 with four " scutella " (? phyllidia), each with two accessory suckers. P. 

 rugosa, Dies., in Platystoma tigrinum from Brazil ; Ephedrocephalus, Dies. 

 Small tetragonal scolex, with phyllidia at the angles. The short neck is 

 dilated to form a flat, octagonal platform, with reflexed edges, from 

 which the scolex arises ; Brazil. Amphoteromorphus, Dies. ; Amphotero- 

 cotyle, Dies. SUB-FAMILY 2. PHYLLOBOTHRINAE, v. Ben. Phyllidia un- 

 armed, more or less complicated by subdivision into " loculi," each 

 phyllidium attached by a narrow base, which is frequently produced to 

 form a peduncle. Echeneiboihrium, v. Ben. (Fig. XVI. 4) ; Rhinebothrium, 

 Lint. (Fig. XVI. 2) ; Spongiobothrium, Lint. ; Anthobothrium, v. Ben. (Fig. 



XVI. 1) ; Crossobothrium, Lint., Anthocephalum, Lint. SUB-FAMILY 3. 

 PHYLLACANTHINAE, v. Ben. Phyllidia armed with booklets. Callio- 

 bothrium, v. Ben. (Fig. XVII. 1) ; C. (Acanthobothrium, v. Ben.) coronatum, 

 Rud. ; C. (Onchobothrium, Blv.) uncinatum, Rud. ; C. (Prosthecobothrium, 

 Dies.) dujardini, Dies. ; Phoreiobothrium, Lint. ; Cylindrophorus, Dies. ; 

 Thysanocephalum, Lint. (Fig. XVII. 2) ; Platybothrium, Lint. ; Pelyoncho- 

 bothrium, Dies. ; P. septicolle, Dies., in Polypterus bichir. FAMILY 2. 

 GAMOBOTHRIDAE, Lint. The four phyllidia united by their lateral 

 margins to form a single discoid or globular mass. Lecanicephalum, 

 Lint. (Fig. XVII. 3, 4). Tylocephalum, Lint, head formed of a globular 

 organ (? united phyllidia) with four accessory suckers, and beyond a large 

 rostellum. T. pingue, Lint, in Ehinopterus ; Discocephalum, Lint (Fig. 



XVII. 5). 



Remarks on the Tetraphyllidea. The anatomy, as well as much 

 of what is known of the life-history of these forms, was investigated 

 by van Beneden, to whose valuable researches we owe so much of 

 our knowledge of parasitic Platy helminths. These Tetraphyllidea 

 are almost exclusively found in the spiral intestine of Selachians, 

 and it appears that here they move about and are not permanently 

 attached as the more highly developed Taeniae are ; this locomotion 

 is effected partly, at least, by the movement of the " phyllidia." 



