PARASITES OF GALVESTON BAY FISHES CHANDLER 133 



sio-ned to the species S. mallev/in^ the adult of which he described in 

 that year, parasitic in the ray Dasyhatis centrura. The larvae were 

 found in a number of salt-water fishes, including Galeichthys mil- 

 lerti. Southwell (1930) referred to this species some adult speci- 

 mens, which he found in rays in Ceylon. Two specimens (U.S.N.M. 

 no. 39523), wdiich I have assigned to this species, were obtained from 

 the mesenteries of Galeichthys fells. 



My specimens seem to agree fairly closely with Linton's descrip- 

 tion and figures of this species except for the smaller size. Unfor- 

 tunately the proboscides are only slightlj' exserted, so a full compari- 

 son of their armature with that described and figured by Linton is 

 not possible. So far as can be seen, however, my specimens agree 

 with Linton's. 



The cysts have an enlarged egg-shaped anterior end measuring 

 about 4 to 5 mm in length and 2.5 mm in breadth. Behind this ante- 

 I'ior portion there is a long tail-like appendage. The scolex and neck, 

 and a bulblike expansion of the body behind the neck, are contained 

 in the enlarged anterior portion of the cyst. The tail consists of 

 a slender prolongation of the body covered by a loose thin sheath, 

 which is a part of the cyst wall. The tail in one specimen is about 

 17 mm long and in the other about 50 mm. The bothria spread out 

 at right angles to the long axis, giving the hammerlike appearance 

 that has been described and figured by Linton. The breadth of the 

 head across the bothria is about 850/x, and the length of the both- 

 ridial portion of the head only about 350/*. A proboscis emerges 

 from near the outer extremity of each bothrium, but none of the 

 proboscides are exserted far enough to show more than one or two 

 basal rows of hooks. The visible hooks consist of very stout thorn- 

 shaped hooks, slender recurved hooks, and numerous minute spines. 

 The proboscides are about 2 mm in length, wath a diameter at the 

 base of about 40/^. The short thick neck is about 560/x in diameter. 

 The contractile bulbs are about 1.2 mm long and 270/x abroad. 



Shipley and Hornell (1906) described and figured under the name 

 T etrarhynchus ylatycefhalus an adult tetrarhynchid that had the 

 head shaped strikingly like G. malleus^ but in which the hooks as de- 

 scribed are like those of G. gig as. In Shipley and Llomell's worm, 

 however, the short proboscides are nearly straight within the head 

 and posteriorly pass to the posterior extremity of the contractile 

 bulbs, in which they lie coiled. In my specimens no such condition 

 exists; the retractor muscles of the proboscides are attached to the 

 anterior ends of the bulbs. It seems certain, therefore, that T. platy- 

 cephalus is identical with neither G. gigas nor G. 'malleus.^ but 

 should be recognized as a third species of Gijmnorhynchus., G. platy- 

 cephalus. 



