58 



From the above description the general similarity to 0. 

 megatyphlon is apparent. The differences briefly stated in 

 resume are as follows: The adult worms are considerably 

 smaller in size than O. megatyphlon (according to our measure- 

 ments of 0. megatyphlon and those of Dujardin; equal 

 according to Rudolphi's, considerably larger according to 

 Schneider's data); and the head is relatively smaller than in 

 0. megatyphlon (our measurements). The papillary emi- 

 nences on the lips are clear and constant; but these are not 

 apparent in O. megatyphlon. The calcareous granules of 

 the cuticular bands and in the walls of the alimentary and 

 genital tubes are constant in 0. megatyphlon, but are uni- 

 formly absent in the case of the present specimens. The 

 fusiform swelling of the esophagus, regarded by Rudolphi 

 as a proventricle, is constant in our specimens of 0. mega- 

 typhlon (Fig. 12); is uniformly absent from 0. microtyphlon. 

 The size of the first part of the intestine (Rudolphi's cecum) 

 is usually smaller than in O. megatyphlon. The vulva is 

 relatively closer to the anus and considerably more anterior 

 to the tip of the tail in the female of 0. microtyphlon (cf. 

 Figs. 5 and 11); and the tail is invariably long and finely 

 drawn out instead of being slightly blunt as in 0. mega- 

 typhlon (in the larval forms of the latter the tail is quite as in 

 0. microtyphlon, and the larvae are practically indistinguish- 

 able). The shape and general appearance of the ova are 

 very similar, but the invariably larger size of those of the 

 smaller worm (compare Figs. 1 and 2) is clear from the 

 material examined by us (and they exceed by one- half to three- 

 fourths the measurements given by Dujardin). Apparently 

 (from camera lucida tracings) the ungulate tip of the tail of 

 0. megatyphlon is slightly larger and is less straight than that 

 of 0. microtyphlon, but the failure to note the finer details 

 of structure of the former prevents close comparison (com- 

 pare Figs. 4 and 10). The difference from the tail of 0. 

 megatyphlon as depicted by Schneider (Fig. 9) is striking. 



The iguana from which the examples in question were 



