NO. 14 MANTER : DIGENETIC TREMATODES OF FISHES 363 



Dactylostomum vitellosum, new species 

 (Plate 36, fig. 35) 



Host: Small, silver tide-pool fish 

 Location : Intestine 

 Locality: Gorgona Island, Colombia 

 Number: One specimen 



SPECIFIC DIAGNOSIS OF DACTITOSTOMUM VITELLOSUM 



Body elongate, smooth, 1.755 by 0.352, widest at about midbody, 

 bluntly rounded posteriorly. Forebody 0.285. Oral sucker 0.119 long; 

 acetabulum 0.180 long, with transverse aperture, each lip of aperture 

 (fig. 35) with 3 large rounded median lobes and 6 small papillalike ele- 

 vations, 3 on each side. Prepharynx very short ; pharynx 0.060 long, 0.076 

 thick; esophagus shorter than pharynx; ceca uniting near posterior end 

 of body, but an anus is apparently lacking. Genital pore median, about 

 midway between suckers. Testes tandem, approximately in midbody, 

 somewhat separated by vitellaria, unlobed but slightly irregular in out- 

 line, somewhat extended transversely; posttesticular space 0.607. Cirrus 

 sac very weak (possibly absent), enclosing only the short cirrus; seminal 

 vesicle tubular, almost straight, free in parenchyma, extending backward 

 to near posterior end of acetabulum. Ovaiy roughly three lobed or heart 

 shaped, median, immediately anterior to testes. Vitelline follicles from 

 anterior border of acetabulum to posterior end of body, chiefly lateral, 

 confluent between and behind testes ; yolk reservoir at dorsoanterior bor- 

 der of ovary; seminal receptacle lacking; uterus preovarian; eggs 53 to 54 

 by 27 to 30 p.. 



Discussion. The genus Dactylostomum was named by Woolcock in 

 1935 and considered to be in the subfamily Coitocoecinae. The type spe- 

 cies is D. gracile from Myxus elongatus. Port Philip Bay, Victoria. Con- 

 sidering the difference in host and locality, the present species is remark- 

 ably similar to D. gracile. It is smaller (1.755 as compared with 2.5 to 

 5.0), there is less difference in the sizes of the 2 suckers, the vitellaria are 

 more profusely developed but have about the same distribution, the phar- 

 ynx is larger, the eggs are smaller (53 to 54 ju, as compared with 70 to 80 

 /x), the posttesticular space is longer. The smaller papillae of the acetabu- 

 lum were not evident in D. gracile, but the extended condition of the 

 sucker may have resulted in their reduction. 



Woolcock compared Dactylostomum with Coitocaecum. The form of 

 the acetabulum suggests Opecoelus and Opegaster. Actually, the genus 



