No. 5 meserve: monogenetic trematodes 57 



Thoracocotyle paradoxica, new species 



(Plate 7, figs. 41-43) 



Host: Scomberomorus maculatus (IVIitchill) 

 Location: Gills 



Locality: Tangoia-Tangola, Mexico 

 Number: 1 



Posterior region of body which functions as a haptor L476 mm. 

 in length by 0.508 in greatest width. The anterior part of the body 

 is attached to the anterior part of the haptor region, 0.712 by 0.288 

 mm. in greatest width. The haptor extends 0.968 mm. to the left and 

 0.508 mm. to the right of the anterior part of the body. Posterior 

 suckers along margins of haptor, eight pairs on posterior part of 

 haptor and six pairs on anterior part. The three pairs on anterior 

 part considerably smaller, as is the sucker at the extreme tip at 

 anterior end of haptor; each one of large suckers, 0.080 mm. in 

 length by 0.100 in width, slightly broader than long. Chitinous 

 framework (fig. 43) typical of the genus with six to ten slender 

 curved pieces imbedded in walls in each side of sucker, one heavy, 

 central I-shaped piece, two lateral curved pieces and one pair on 

 each side at distal end of sucker, curved downward. Two pairs of 

 hooks at posterior tip of haptor, outer pair longer, slender, rela- 

 tively straight with short recurved points and process at middle, 

 0.048 mm. in length; inner pair posterior, arcuate and, in shape, 

 resembling a small hand scythe with short handle, 0.016 mm. in 

 length. Slightly anterior to hooks are six conspicuous nuclei, deeply 

 staining with heavy nuclear membranes and prominent eccentric 

 nucleoli. Mouth ventral, slightly subterminal. Anterior mouth suck- 

 ers elliptical, without septa, broader than long, 0.024 mm. in length 

 to 0.044 mm. in width. Pharynx muscular, bulb-shaped, 0.052 mm. 

 in length by 0.035 mm, in width. Rest of digestive system not visible. 

 Genital pore just posterior to pharynx in mid-line, unarmed. Testes 

 seven in number, smooth, unlobed, longer than wide, in mid-line 

 posterior to ovary, close together and in one row. Vas deferens a 

 broad tortuous tube in mid-line. Cirrus rudimentary, unarmed. 

 Ovary shaped like inverted U in mid-line between seventh pair of 

 suckers counting from posterior end. Shell gland large, spherical, 

 posterior to ovary. Vitellaria in two groups, one in anterior part of 

 haptor and one in posterior part, confluent anteriorly and posteriorly. 



