6 BULLETIN 140, UNITED STATES NATIONAL MUSEUM 



absent; if absent the mouth is usually a simple structure with cephalic 

 papillae, but without the 2 distinct lateral lips of the spirurids or the 

 3 distinct and prominent lips of the ascarids and oxyurids. Males 

 with 2 spicules and females usually with 2 ovaries (the Heligmo- 

 somidae and Ollulaninae having but one ovary). Vulva situated 

 anywhere from anterior to posterior body region. Oviparous or 

 ovoviviparous. First-stage larvae rhabditiform except in meta- 

 strongyles, in which case filariform. 



This suborder is here held to include all of the bursate nematodes. 

 The grouping of all such forms is warranted on the very distinctive 

 and important bursa. At the same time it is recognized that the 

 group includes groups of apparent wide divergence on such char- 

 acters as musculature and form of larval development. 



KEY TO SUPERFAMILIES OF STRONGYLATA 



1. Polymyarian ; usually in respiratory or circulatory tract; the bursa is re- 



duced, in relation to the size of the worm, by comparison with typical 

 members of the other superfamilies, and the dorsal ray is often very much 

 wider than the other bursa rays ; in rare instances the bursa is lacking. 



Metastrongyloidea, p. 7. 

 Meromyarian ; usually in digestive tract as adults, but sometimes in respira- 

 tory tract (Synffamus), circulatory system (Stronffylits), or tissues 

 (Stephatiurus) as adults or agamic forms, and often in such locations as 

 larvae or agamic individuals ; bursa typical, relatively large, and with the 

 dorsal ray approximately as wide as other members of the bursa rays. 2. 



2. Buccal capsule present ; usually relatively thick forms ; usually in digestive 



tract, sometimes in respiratory system or tissue as adults. 



Strongyloidea, p. 29. 



Buccal capsule absent or present as a much-reduced structure (Amidos- 



toinum) ; usually relatively slender and sometimes hair-like forms; always 



in digestive system Trichostrongyloidea, p. 7. 



It appears necessary to restrict the limits of the superfamily 

 Strongyloidea to those of what has been the family Strongylidae 

 and to create two new superfamilies from the old Strongyloidea as 

 defined by Hall in assigning superfamily rank to this group. The 

 lines of demarcation which previously existed, separating all forms 

 with a distinct buccal capsule, as the Strongylidae, from all those 

 without a distinct buccal capsule, the Trichostrongylidae and Meta- 

 strongylidae, have been broken down by the formation of such new 

 families as the Syngamidae, Diaphanocephalidae, etc. These latter 

 have a buccal capsule and should again be coordinated with the 

 now restricted Strongylidae. In order to reestablish this grouping 

 on the basis of the presence or absence of a buccal capsule, the 

 present writer has restricted the superfamily Strongyloidea, here- 

 tofore including all the bursate nematodes, to those families which 

 possess a buccal capsule, and is creating the coordinate superfami- 

 lies Trichostrongyloidea and Metastrongyloidea for those without 



