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 



Phoreioboth- 



rium lasium 



(Linton). 



Scolex without hooks; bothria usually stalked and with 

 or without septa subdividing them, and with or without a 

 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 Phyllobothriidae here described: 



a* Bothria without transverse septa and myzorhynchus. 



&! Bothria without accessory suckers 1. ANTHOBOTHEIUM 



& 2 Bothria with accessory suckers. 



Ci Each bothrium with 2 suckers 2. OEYGMATOBOTHEIUM 



C 2 Each bothrium with 1 sucker. 



d^ Edges of bothria not or but little convoluted 3. CBOSSOBOTHBIUM 



d z Edges of bothria very much convoluted 4. PHYLLOBOTHRIUM 



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



1. ANTHOBOTHRIUM van Beneden. Bothria very contractile, oval 

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

 suckers; body elongate: several species. 



A. laciniatum 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. ORYGMATOBOTHRITJM Diesing. Bothria stalked, 

 with a larger accessory sucker in the middle and a 

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

 confluent; neck long: several species. 



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. CROSSOBOTHRITJM 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. 



Fig. 318 



Crossobothrium 



laciniatum 



(Curtis). 



