CESTODES 195 



walls, or may be subdivided into 2 portions, of which the hinder may have 

 the appearance of a separate sucker; a pseudoscolex may also take the 

 place of the scolex; uterus usually an extensive sac, which may occupy 

 the greater part of the segment with a ventral opening; pore for cirrus 

 and vagina either marginal or dorsal: 7 genera; in fishes. 



1. ABOTHRITJM van Beneden. Suckers shallow; a cylindrical pseudo- 

 scolex may be present in place of the scolex, the hinder margin of 

 which is prolonged backwards so as to project over the strobila; seg- 

 mentation of hinder part indistinct; cirrus and vaginal pores marginal, 

 that of uterus medium: 3 species. 



A. rugosum (Batsch). Length 25 cm. or more; breadth 4.7 mm.: 

 in the intestine of the cod; often common. 



2. BOTHRIOCEPHALUS Rudolphi (Dibothrium Diesing). Scolex elon- 

 gate with rather weak suckers; no accessory suckers; segmentation 

 often indistinct; neck not present; uterine opening mid ventral; common 

 genital pore for cirrus and vagina middorsal: about 4 species. 



B. lacinatus (Linton). Body 15 cm. long, 4 mm. broad in the 

 middle, tapering towards hinder end ; segmentation distinct, the posterior 

 margins of the proglottids projecting backwards, making the margin of 

 the strobila serrate : in Tarpon atlanticus. 



ORDER 2. TETRAPHYLLIDEA. 



Scolex with 4 bothria, which vary much in form, being either stalked 

 or not and with or without hooks and accessory suckers; a pseudoscolex 

 may replace the scolex; segmentation distinct; cirrus and vagina open on 

 the margin; no uterine pore; yolk glands paired: 4 families and about 

 30 genera; in selachians, and also in other fish, amphibians, and reptiles. 



Key to the families of Tetraphyllidea here described: 



! Hooks present at the forward end of each bothrium .... 1. ONCHOBOTHBIIDAE 

 a z No such hooks 2. PHYLLOBOTHRIIDAE 



FAMILY 1. ONCHOBOTHEIIDAE. 



Hooks of various shape present in the anterior rim of the bothria; 

 bothria either sessile or with short stalks; accessory suckers usually 

 present ; the segments usually detach themselves before sexual maturity : 

 in spiral valve of selachians; 9 genera. 



1. CALLIOBOTHRITJM van Beneden. Bothria elongate, each being 

 divided by 2 transverse septa into 3 divisions of unequal size and with 

 either 1 or 3 small accessory suckers and 2 or 4 simple hooks: several 

 species. 



C. verticillatum (Rudolphi). Length up to 15 cm.; length of ter- 

 minal segment about 3.5 mm., width 1.7 nun. ; a 3-lobed accessory sucker 

 and 4 hooks in front of each bothrium; body very slender, resembling 



