KO.2350. NEMATODE GENV8 NEMATODIRUS—MAY. 579 



larger dorsal and two smaller latero- ventral teeth. Nerve ring near 

 middle of esophagus. Cervical papillae minute or absent. Ex- 

 cretory pore large, opening on ventral side near base of esophagus 

 and connected with two unicellular glands closely associated with the 

 lateral lines and occupying the anterior fifth of the body. Bursa 

 nearly terminal, with two large lateral, symmetrical lobes and two 

 small dorsal lobes, each closely associated with a lateral lobe. No 

 unpaired median dorsal lobe. Ventral rays of bursa slender, close 

 together, parallel. Externo-lateral ray proximally close to medio- 

 lateral ray, but distally curved ventrad, away from the latter. 

 Medio-lateral and postero-lateral rays close together, diverging 

 slightly at the tip and curving slightly dorsad. Lateral rays much 

 thicker than others. Externo-dorsal ray very slender. Dorsal ray 

 (one in each dorsal lobe) short, bifid at the tip, with the external 

 branch curved toward externo-dorsal ray. Spicules slender, tubular, 

 united by a membrane throughout part of their length. Prebursal 

 papillae small, inconspicuous. 



Females larger than males. Vulva a transverse slit located in or 

 near the middle third of the body. Eggs large, oval. Posterior end 

 of female truncate, provided with a short, slender, acutely pointed 

 process. 



Type species. — Nematodirus fiUcollis (Rudolphi, 1802) Ransom, 

 1907. 



The genus M ecistocirrus Railliet and Henry, 1912, with M. digita- 

 tus (von Linstow, 1906) Railliet and Henry, 1912, as type species, 

 is very closely related to Nematodirus. In it the vulva of the female 

 is located near the anus. 



KET TO SPECIES OF NEMATODIEUS. 



1(12). Spicules less than 2 mm. long 2. 



2(3). Spicules not united at tip furcatus. 



3(2). Spicules united at tip 4. 



4(7). Dorsal lobes of bursa not distinctly set off from lateral lobes; spicules 



with sharp point 5. 



5(6). Medio-lateral and postero-lateral rays of bursa scarcely separated ; 



eggs with smooth shells fiUcollis. 



6(5). Medio-lateral and postero-lateral rays of bursa well sepai*ated ; eggs 



with alveolate shells roscidus. 



7(4). Dorsal lobes of bursa more or less distinctly set off from lateral lobes; 



spicules with sharp or blunt point 8. 



8(9). Spicule point blunt or spatulate spathiger. 



9(8). Spicule point sharp 10. 



10(11). Spicules of equal length, straight at tip, with no tendency toward 



twisting helvetianus. 



11(10). Spicules slightly unequal in length, twisted near the tip abnormalis. 



12 (1). Spicules more than 2 mm. long 13, 



13(14). Vulva in anterior half of body dromedarii. 



14(13). Vulva in posterior half of body 15, 



15(16). Eggs large, 250 by 110 m; spicules 5 mm. long mauritanicus. 



16(15), Eggs smaller, 175 by 85 /i; spicules 3 mm, long neotoma. 



