PARASITES OF GALVESTON BAY FISHES CHANDLER 131 



those of Gymnorhynchus gig as. Further remarks on T etrarhynchus 

 plafycephaliis -will be found in the discussion of Gymnorhynchus 

 malJeus. 



Three specimens of larval tetrarhynchids (U.S.N.M. no. 39522) 

 from Galveston Bay fishes have been assigned to this species; two 

 were found encysted on the mesenteries of Galeichthys felis, a single 

 one in each of two hosts, Avhile the third was found encysted in the 

 body cavity of a croaker {Micropogon undulafus). When the cysts 

 were burst the very characteristic larvae were freed; these larvae 

 consist of a head and neck, followed by a nearly spherical vesicle 

 into which the head and neck may be withdrawn, and then a long 

 tail-like portion. Such larvae, probably all belonging to the same 

 species, have been figured under the names Gy??i?iorhynchus reptans 

 and Anthocephalus inacrourus by Bremser (1824) ; under the name 

 Pterohothnum heteracanthujii by Diesing (1855) ; as a '■'■ Tetrdboth- 

 rium larva" by Linton (1887); as a Syndesmohothrium filicoUe by 

 Linton (1889); and as Gymnorhynchus glgas by Southwell (1930). 

 The larvae reported by Southwell that lack a vesicle in the neck 

 should not, I think, be referred to this species. Dollfus (1929b) con- 

 siders Pterohofhrium Diesing, 1850 (later renamed Synhothinum, and 

 still later SyndesmohothrJum) as a valid genus distinct from Gym- 

 norhynchus., but his reasons for doing so are not clear. 



Since there is so much confusion with respect to this species it 

 seems desirable to describe some of the details of the specimens 

 found in Galveston Bay fishes, and then to point out the features 

 actually characterizing the species. 



The vesicle in which the scolex lies measures, in my specimens, 

 2.5 to 3.5 mm in length and is about three-fourths as wide as long. 

 The relations of scolex, vesicle, and " tail " are precisely as de- 

 scribed by Linton in 1887. The tail is several centimeters in length 

 and about 0.75 mm in breadth. The four bothria are mobile, spread- 

 ing from the front of the head, 'jacli with a sucking disk; they 

 measure about 300/x in an anteroposterior direction, while the width 

 of the head across the bothria is about 450^ to 470|Li. The neck 

 anterior to the contractile bulbs (pars vaginalis of Pintner, 1913) 

 is 2.4 mm long and about 200/x broad, widening out in the bulbar 

 region to about 400ja (pi. 8, fig. 1). The neck is slightly dilated 

 just anterior to the bulbs, where the proboscis sheaths are coiled. 

 The postbulbar region is shorter than the pars vaginalis but varies 

 in my specimens from about 0.5 to 1.5 mm, according to the state 

 of contraction. The bulbs are elongate and of nearly uniform 

 width, measuring about 1 to 1.3 mm in length by about 135;u, in 

 width. The total length of the proboscides, judged by the extent 

 of the inverted spines, is about 3 mm; the diameter, exclusive of 

 the spines, is about 60;^. The proboscis sheaths are straight in the 



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