NO. 14 MANTER : DIGENETIC TREMATODES OF FISHES 431 



shallow water. The above records do not constitute clear evidence against 

 such a view, since the temperature of the water at Tagus Cove is approxi- 

 mately 68° F. 



A specimen of a Derogenes species which may be D. various was col- 

 lected from an unidentified flounder dredged at Bahia Honda, Panama. 

 The exact depth from which this fish was secured is not available, but no 

 very deep hauls were made. If this specimen actually is D. varicus, it 

 occurs in rather warm water. However, eggs in this specimen were 68 

 to 69 by 27 to 29 /x, which is markedly larger than the 51 to 56 by 29 to 

 31 size of specimens from Tagus Cove. Egg size in D. varicus is evidently 

 variable, records varying from 51 to 66 by 28 to 40 /x. Since the Panama 

 specimens (2) exceed even these limits, it is identified merely as Dero- 

 genes species. 



Theletrum lissosomum, new species 

 (Plate48, figs. 119-121) 



Host: Unidentified angelfish 



Location: Stomach 



Locality : Socorro Island, Mexico 



Number: 7 from one fish, one from another 



SPECIFIC DIAGNOSIS OF THELETRUM LISSOSOMUM 



Body smooth, elongate, cylindrical, without ecsoma, with ventral 

 papillae. Length 2.916 to 3.699; greatest width 0.216 to 0.499. Fore- 

 body 0.607 to 0.712 (about y^ body length), tapering slightly to a 

 rounded end. Hindbody almost equally wide, posterior end bluntly 

 rounded, almost truncate. Oral sucker subspherical, 0.180 to 0.195 in 

 transverse diameter. Acetabulum 0.255 to 0.300 in transverse diameter, 

 somewhat longer than wide, with longitudinal aperture. Sucker ratio 

 approximately 2:3. Pharynx 0.085 to 0.111 in length by 0.080 to 0.099 

 in width; esophagus short, with small ventrally directed esophageal di- 

 verticulum; intestinal bifurcation nearer oral sucker; ceca rather wide, 

 extending to extreme posterior end of body beyond uterine coils. Genital 

 pore median, varying from opposite middle of pharynx to opposite intes- 

 tinal bifurcation. Testes globular, oblique, ventral to ceca, about halfway 

 between acetabulum and ovary, separated by uterus. Seminal vesicle 

 inconspicuous, tubular, sinuous; its posterior end near anterior edge of 

 acetabulum. Prostatic gland well developed; pars prostatica almost 

 straight, shorter than seminal vesicle, near intestinal bifurcation. Sinus 



