150 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.50. 



reply Professor Railliet stated that he Avas unable to locate any 

 material of the species in question, but that the species was created 

 to replace M etastrongylus Molin, 1861a. Professor Railliet called 

 attention to the fact that in his generic diagnosis of M etastrongylus^ 

 Molin (1861ff) gives as a leading feature the presence of one ovary 

 and uterus in the female, and that Stiles and Hassall (1905) in 

 selecting a type-species of M etastrongylus selected M etastrongylus 

 paradoxus, on the ground that it was the common and available 

 species, overlooking the fact that Railliet (1893) had already pointed 

 out that Molin was in error in stating that M. faradoxus had but a 

 single ovary. The generic characters being fixed by the type-species, 

 it becomes necessary to create a new genus for the forms with a single 

 ovary which Molin had in mind in creating the genus Metastron- 

 gylus. With this explanation available it is readily evident that 

 the new genus is quite important, so much so that Travassos has 

 very properly made it the type of a new subfamily. 



Type-species. — TIeligmosonium costellatuin (Dujardin, 1845) Rail- 

 liet and Henry, 1909«. 



ANALYTICAL KEY TO SPECIES OF HELIGMOSOMUM 



1. Males over 10 niiii. juid females over 15 mm. long. 



Hcligmosomum costellatum, p. 150. 

 Males less than 10 mm. and females less than 15 mm. long 2. 



2. Males not over 2.25 mm. long ; females less than 2.5 mnl. long. 



Eeligmosomiim ininiitum, p. 151. 

 Males over 2.25 mm. ; females 2.5 mm. long or longer 3. 



3. Males over 5 mm. long ; females over S mm. long ; with large cervical alae. 



HeUgmosomum gracile, p. 153. 



Males not over 5 mm. long; females not over 8 mm. long; or larger forms 



without cervical alae . 4. 



4. Males 4.5 to 5 mm. long ; females 6.4 to 8 mm. long ; spicules 600 to G75 fj. long. 



Hcligmosomum laeve, p. 153. 



Males not over 3.5 mm. long; females not over 4.37 mm. long; spicules less 



than 580 fi long 5. 



5. Males 2.6 to 2.8 mm. long and females 3.5 mm. long; spicules 550 to 560- /* 



long HeUgmosomum hraziUense, p. 154. 



Males 2.5 to 3.5 mm. long and females 3.44 to 4.37 mm. long; spicules 360 

 to 440 n long HeUgmosomum vexiUatvm,i>.15o. 



The principal tangible differences in the descriptions of species of 

 HeUgmosomum are in regard to size, and these differences have been 

 used in the foregoing key. If the published figures of the bursae were 

 used, it is doubtful whether the species would appear to have any- 

 thing like generic relation. 



HELIGMOSOMUM COSTELLATUM (Dujardin, 1845) Railliet and Henry, 1909a. 



Synonyms. — Strongylus costellatus Dujardin, 1845; M etastrongy- 

 lus costellatus (Dujardin, 1845) Molin, 1861a; Strongylus polygyrus 

 Dujardin, 1845, of Stossich, 1899. 



