CESTODE PARASITES. 269 



Syndesmobothrium, Diesing (11). 



Body articulate, taeniaeforni. Neck tubular, rounded at base. Head tetragonal, with four terminal 

 prominent bothi'ia attached to the head by posterior margha, cruciformly disposed, oval, shghtly convex, 

 joined with each other at the base by a membrane, proboscides four, filiform armed, each one running 

 tlxrough a bothrium (pedicel) excurrent at apex, long, retractile in the neck. Genital apertures marginal (?). 

 In intestines of marme fishes of tropical America. 



Syndesmobothrium filicolle, Linton. (Plate II., Figs. 16 and 17.) 



I have no hesitation in referring to this species a number of larval forms obtained from the 

 intestines of Gybium guttatum and Chorinemiis lysan. 



The head is squarisli in front view, with a bothrium at each corner. The bothridia are oval or 

 <3up-shaped. The larvae agree in every detail with Linton's figure of this species, save that in our types 

 the exit of the proboscides was closed. The proboscis sacs were marked with fine criss-cross Hnes, only 

 visible imder a liigh power. 



Habitat. — (i.) The mesenteries of CAonmemMS Zj/^arj. February 25, 1911. Forty-five specimens. 

 These larvae were enclosed in tadpole-shaped cysts, the cysts measuring on an average 25 mm. by 2 • 5 mm. 

 The larvae was contained in the " head " part of the cysts, which in preserved specimens were of a yellow 

 colour. The rest of the cyst was wliite, membraneous, and transparent. The larvse measured 2 mm. 

 by ■ 5 mm. 



(ii.) The mesenteries of Cybium guttatum. November 27, 1910. Fifty-five specimens, same as 

 preceding. 



I beheve these specimens to be the same as those described by Shipley and Hornell from Cybium 

 guttatum, in Part V., " Ceylon Pearl Oyster Reports," Plate III., Fig. 43. 



It is interesting to note that Linton states that he has " met with encysted forms similar to this 

 (Srjiidesmoboihrium filicolle) in various species of the Teleostei, such asPomatomus saltatrix, Cybium regale, 

 &c. One from Spanish mackerel {Cybium regale) was described by mo in the ' American Naturalist ' 

 for February, 1887, under the name of larval Tetrarhynchobothrium." 



The occurrence of this larva in these Teleosts raises the question as to the position of tliis stage in 

 the life-history of the parasite. On the whole, I feel confident— and I have every reason to believe— that . 

 the larvas normally inhabit the tissues of either crabs or molluscs, and have their adult stage in some 

 Elasmobranch. The presence of the larvse in these Teleosts is due to their feeding on crabs or molluscs, 

 but the larvse does not develop any further in them than in crabs or molluscs. But if either the fish 

 containing these cysts derived from crabs and molluscs, or the crabs and molluscs themselves, be eaten 

 by an Elasmobranch, then m every case the larva would attain the adult form in the Elasmobranch. 



The stage found in these fish is probably not intermediate, but casual and accidental. These fish 

 are not to be regarded as intermediate but as accidental hosts. 



Tetbaehynchus, Rudolphi. 

 Body articulate, tseniaeform. Neck tubular. Head with four bothria in two lateral pau-s, 

 parallel with the head. Proboscides four, termmal, filiform, ai'med, retractile in the neck, free, i.e., not 

 running through tlie botliria. Genital apertures marginal or lateral. 



Tetrarhynchus gangeticus, Shipley and Hornell (20). (Plate II., Fig. 18.) 

 I refer with some hesitation four larval forms to the above species. They correspond with 



T. gangeticus in size, in the proboscis tubes being bent in and out and not spirally twisted, and in- the 



size and shape of the bothridia. The hooks are also similar. 



Habitat.— The mesenteries of Sphyrcena jello. February 27, 1911. Four cysts, measurements as 



follows : (1) 32 mm. long, 6 mm. broad ; (2) 30 mm. long, 5 mm. broatl ; (3) 26 nun. long, 5 mm. 



broad; (4) 14 mm. long, 4 mm. broad. 



