194 FILARIOIDEA 



about too wide a separation of groups which, when considered 

 together, are obviously closely related to each other. On 

 this account we have included in the Filarioidea the forms 

 which have been regarded by some authorities as forming a 

 superfamily Spiruroidea, or a suborder Spirurata. 



Similarly, the difficulty of finding characters common to 

 all the members of a family, and yet of sufficient importance 

 to separate it from another family, has led us to discard 

 certain families, and to reduce others to the rank of sub- 

 families. Thus, to take an example, when the characters 

 common to the Acuariinae and the Physalopterinae are 

 reviewed, it is evident that the family Acuariidae is indis- 

 tinguishable from the family Spiruridae, and it has accordingly 

 been suppressed. 



Fam. 1. FILARIIDAE Glaus, 1885. 



Body usually filiform and much elongated. Head with 

 two lateral and four submedian papillae. Mouth usually 

 without lip-like structures. A simple buccal capsule rarely 

 present. Oesophagus usually with a short anterior muscular 

 portion and a long and thicker posterior glandular portion. 

 Spicules two, usually unequal and dissimilar. Vulva towards 

 the anterior end of the body. Adults in connective tissue, 

 blood-vessels or serous cavities of Vertebrates. 



Subfam. 1. FILARIINAE Stiles, 1907. 



Head without epaulette-like structures. Oesophagus 

 typical. Spicules unequal and dissimilar. Adults in con- 

 nective tissue, serous cavities or blood-vessels of Vertebrates. 



The subfamily Onchoeercinae Leiper, 1911, does not appear to be 

 a natural group. It is based upon the presence of the spiral thickenings 

 of the cuticle characteristic of Onchocerca. This character does not 

 occur in any of the other genera that have been referred subsequently 

 to the subfamily. Moreover, it is a character that hardly seems to 

 warrant the separation of Onchocerca itself from tlie subfamily Filariinae. 

 We have accordingly suppressed the subfamily Onchoeercinae, and 

 have included all its genera among the Filariinae. 



1. Filaria Miiller, 1787. 



Cuticle thick, smooth. Mouth small, with six large papillae* 

 (two lateral, four submedian). In the male two additional 

 pairs of small submedian papillae anterior to the former, and 

 in the female one pair of small subventral papillae just pos- 

 terior. Oesophagus short, not distinctly separated into 

 glandular and muscular parts. Tail of male spirally twisted, 



* According to Seurat (1920) F. mar. is has, in addition to six small 

 cephalic papillae, four lips, two of which are lateral, one dorsal and 

 one ventral. 



