May 17,1924 A New Nematode 667 
Strongylus. 
1. No teeth in mouth capsule_ S. edentatus. 
One or more teeth in mouth capsule_2. 
2. Teeth on both the dorsal and ventral walls of mouth capsule. _ S. equinus. 
Only one bifurcated tooth on dorsal wall of mouth capsule_3. 
3. Male not over 16, female not over 24 mm.;excretory pore at level of nerve 
ring; the two lobes of the tooth are high and have smooth margins. 
S. vulgaris. 
Male 18-32 mm., female 30-43 mm.; excretory pore close behind mouth 
collar; the two lobes of the tooth low and broad and margins divided into 
rounded cusps_ S. asini. 
Triodontophorus. 
1. Median lobe of bursa long; teeth of pharynx usually not denticulated_2. 
Median lobe of bursa short; teeth usually denticulated_3. 
2. Male not over 13, female not over 14 mm. long; mouth collar depressed at 
margin; vulva 535-700 m from posterior end; tail region conical. T. minor 
Male 13.5-14, female 16-17 mm. long; mouth collar erect at margin; vulva 
270-300 m from posterior end; tail region very blunt, obliquely truncated. 
T. brevicauda . 
3. Tail region of female short; vulva 460-560 m from end; spicules 1.25 mm. 
long; mouth capsule small, length not more than 90 m, breadth not more 
than 140m _ T. tenuicollis . 
Tail region of female elongated; vulva 1.4 to 2 mm. or more from end; 
spicules 3.5-4 mm. long; mouth capsule of moderate size, length 100- 
130 m, breadth 150-180 m_4. 
4. Male 14.5-15.5 mm., female 16.5-18.7 mm. long; mouth collar high, circular 
in profile; vulva 1.4-1.7 mm. from end; spicules have stout barbs. (G. 
Theiler says this is a synonym of T. serratus .)_ T. intermedius . 
Male 18 mm., female 25 mm. long; mouth collar low and somewhat de¬ 
pressed at margin; vulva more than 2 mm. from end; spicules do not 
have barbs__ T. serratus . 
Gyalocephalus. 
1. Genital cone extends only to free margin of bursa_ G. capitatus . 
Genital cone extends beyond margin of bursa; length of cone usually twice 
as great as preceding species___ G. equi. 
Oesophagodontus. 
Males 15-16 mm., females 19-22 mm. long; mouth capsule goblet-shaped; 
external leaf crown composed of 18 large, projecting elements; internal 
leaf crown of 36-48 slender elements; dorsal lobe of bursa lacking; 
postero-lateral ray branched at base; posterior extremity of female straight, 
gradually tapering from vulva region to tip (a length of 2.3-3 mm.) 
Oesophagodontus robustus. 
POTERIOSTOMTJM. 
1. All the elements of the internal leaf crown of equal size; distance of vulva 
from anus 925 m to 1.5 mm_ P. ratzii . 
All the elements of the internal leaf crown not of equal size (2 lateral and 
4 submedian elements being longer than the others); distance of vulva 
from anus 680 to 825 m_2. 
2. Seven small leaf elements between each of the elongated ones. 
P. imparidentatum. 
Ten small leaf elements between each of the elongated ones. 
P. pluridentatum. 
96037—24t-5 
