205] PROTEOCEPHALIDAE—LA RUE 205 



served in formol the writer (1911) has proposed the specific name 

 Ophiotaenia perspicua. Other specimens of this species were furnished 

 the writer by Mr. Herman Douthitt from Natrix (Nerodia) rhombifer 

 taken in Oklahoma, June, 1910. 



La Rue (1911 :480) described this species in a preliminary way and 

 made it the type of his new genus Ophiotaenia. 



Two heads of the lot from Oklahoma measured respectively 0.374 

 mm. and 0.340 mm. broad by 0.27 mm. thick. The suckers measured 

 0.119 mm. long by 0.102 mm. broad. The neck was 0.272 mm. broad 

 and several millimeters long. The longest worm was 135 mm. long by 

 a maximum breadth of 1.19 mm. Specimens were mounted in toto and 

 from them a positive determination was made. The longest specimen 

 of the preserved type material measured 36.0 cm. in length by a maxi- 

 mum breadth of 2.0 mm. The neck is long, slightly broader than the 

 head and not easily distinguished from the segmented portion following. 

 The first proglottids are very short. About 16.0 cm. from the head the 

 proglottids are quadrate, length and breadth being about 2.0 mm. These 

 proglottids are mature. At 26.0 cm. from the head the proglottids 

 begin to increase in length and to decrease in breadth. The second from 

 the last proglottid measures 3.8 mm. long by 1.2 mm. broad. These 

 proglottids are ripe. An examination of other specimens of the lot 

 shows a considerable variation in dimensions. Proglottids are attached 

 by their full width. The margins of the strobila are smooth, almost 

 without indentations at the junction of the proglottids. As a conse- 

 quence the segmentation is indistinct so that without staining and clear- 

 ing the proglottid limits are made out with difficulty even with a 

 microscope. The proglottids are rectangular in shape, rarely oval. The 

 surface of the worm is sometimes thrown into shallow longitudinal fur- 

 rows. No transverse furrows are noted. In life and when preserved in 

 formol the specimens are translucent from which character is derived 

 the specific name. 



The head is somewhat conical in shape, slightly flattened dorso- 

 ventrally and marked off into four quadrants by grooves which extend 

 from the basal region to, or nearly to, the apex. Each quadrant bears 

 at its thickest and broadest region a sucker which opens outward and 

 slightly forward. The apex does not exhibit a circular depression or a 

 fifth sucker. The head varies in breadth from 0.255 mm. to 0.408 mm. 

 This dimension slightly exceeds the thickness and length. A head 0.357 

 broad measured 0.306 mm. in thickness, while a head 0.408 mm. broad 

 was about 0.270 mm. long. 



The suckers show also considerable variation in size and shape. In 

 general they are nearly round or oval in outline with shallow cavities. 



