3J.D A NEW NEIIATODE PARASITE OP A LIZARD, 



albatross, Diomedea exulans), and has recently been raised to a new genus, Seu- 

 ratia, by Skrjabin (1916). He places it in the family Acuariidae, subfamily 

 Acuariinae, and points out that it is identical with the species described by Lin- 

 stow as Rictularia paradoxa and by Seurat as Acuaria ptelagica. 



The spines in the new form, from the lizard, differ entirely in character and 

 arrangement from those described for the genus Seuratia; and, in the general 

 structure of the body, it presents closer affinities with the Physalopterinae than 

 with the Acuariinae. 



It agrees with the genera Phifsaloptera and Rictularim in the structure of the 

 oesophagus, the position of the nerve-ring, post-cervical papillae and excretory 

 pore, the anterior situation of the vulva, the conformation of the various parts 

 of the female genital system, and the eggs containing well developed embryo when 

 oviposited. The cephalic collarette, though poorly developed, and the lateral 

 lips, especially the right lip with its median tooth, recall those of Physaloptera. 

 But the asymmetrical character of the lips, and the presence of a cuticular 

 ornamentation of spines on the body separate it from Physalopterai The deep 

 groove and ridge dividing the head end from the rest of the body suggest affinities 

 with Gnathostoma, but the anterior end of the body is not swollen, and the 

 spines are quite differently arranged, while the vulva is situated very anteriorly, 

 instead of behind the middle of the body as it is in the Gnathostomidae. 



As already noted, Rictularia disparilis agrees with the descriptions given by 

 Froelich and Dujardin of the type species of the genus, R. cristata, in having 

 a single row of spines, of uniform character, set close together and situated asym- 

 metrically on one side of the body; it differs, however, in the continuity and 

 length of the row, which is not confined to the region in front of the vulva, as 

 described for R. cristata. Modern writers have doubted the correctness of the 

 accounts given by Froelich and Dujardin, although Dujardin specially emphasises 

 the statement "une rangee non symmetrique." All the other species assigned to 

 the genus have two rows of combs and spines, one down each side of the body, 

 with a distinct difference between anterior combs and posterior spines. Hall 

 • (1914, 1916) concludes that the original descriptions of the type species are based 

 on imperfect observation, and that R. cristata had really two latero-ventral rows 

 of spines, of which only the upper and nearer row was seen. Accordingly, 

 Jagerskiold (1909) and Hall (1914), in their generic diagnoses include "two 

 latero-ventral rows of comb or spine-like structures." But they point out that if 

 Froelich's description should be confirmed, the generic diagnosis would need re- 

 vision, and it would be necessary to establish a new genus for all the other species 

 at present assigned to the genus. 



Although Froelich's species was taken from a rodent, and the other species 

 found in rodents, as well as in carnivores, possess two spine rows, the discovery 

 of this new form from a lizard, which undoubtedly has only a single asym- 

 metrical row, suggests the possibility that Froelich's and Dujardin's observations 

 may ha,ve been correct. 



Rictularia disparilis, however, differs from the other species included in the 

 genus in another important character, namely, the structure of the buccal cavity 

 and the position of its aperture. 



It has been assumed that in Froelich's species the aperture is dorsal, as 

 it is in the other species described. Accordingly, the diagnosis of the genus 

 given by Hall defines the mouth opening as "more or less distinctly dorsal, and 

 witli its base armed with teeth and spines." In R. disparilis, owing to the asyni- 



