196 



PLATHELMINTHES 



a white hair ; scolex the size of a small pinhead : often common in spiral 

 valve of the smooth dogfish. 



2. Phoreiobothrium Linton. Bothria rectangular and elongate, 

 without subdivisions; an accessory sucker and 2 three-pronged hooks 

 at the forward end of each bothrium; neck long, with 

 minute spines: 1 species. 



P. lasium Linton (Fig. 317). Length 4 cm.; terminal 

 segment about 2.2 mm. long and .84 mm. wide: in spiral 

 valve of the dusky shark. 



Family 2. PHYLLOBOTHEIIDAE. 



Fig. 317 



Scolex of Scolex without hooks ; bothria usually stalked and with 



Photeiohoth' , _ ._ , i • , 



rium lasium or Without septa subdividmg them, and with or without a 



(Linton). . . 



myzorhynchus, which is a central, stalked sucker rising 



from midst of the bothria, and other accessory suckers: about 12 genera. 



Key to the genera of Phyllohothriidae here described: 



Oi Bothria without transverse septa and myzorhynchus. 



&i Bothria without accessory suckers 1. Anthobothbium 



62 Bothria with accessory suckers. 



Cj Each bothrium with 2 suckers 2. Orygmatobothbium 



Cj Each bothrium with 1 sucker. 



di Edges of bothria not or but little convoluted 3. Crossobothbium 



d^ Edges of bothria very much convohited 4. Piiyixobotiirium 



a, Bothria with 2 septa and with a myzorhynchus 5. Echeneibothrium 



1. Anthobothrixjm van Beneden. Bothria very contractile, oval 

 in shape, stalked, their edges not or but little folded; without accessory 

 suckers; body elongate: several species. 



A. laciniatmn Linton. Length up to 21 mm.; length of terminal 

 segment about 1.8 mm., width 1 mm. : in spiral valve of 

 sand shark and other sharks; often numerous. ^^. 



2. Orygmatobothrium Diesing. Bothria stalked, 

 with a larger accessoiy sucker in the middle and a 

 smaller one at the forward end of each, which may be crolsobom-ium 

 confluent; neck long: several species. ^(CurSs)?* 



0. paulum Linton. Length 9 mm. ; breadth of ter- 

 minal segment about .28 mm., length 1.03 mm.: in spiral valve of the 

 tiger shark; often very numerous. 



3. Crossobothrium Linton. Bothria stalked, each with an acces- 

 sory sucker at the forward end, and with its rim more or less convo- 

 luted; body elongate: 1 species. 



C. laciniatum Linton (Fig. 318). Length up to 25 cm.; segmenta- 

 tion occurs at certain times in both directions, making the middle segments 

 the youngest: in the spiral valve of the sand shark; common. 



