4O NORTH AMERICAN 



from one end to the other, and diametral lines at the base of the 

 pharynx, the nerve-ring, the end of the neck, at the vulva in fe- 

 males and at the middle in males, and finally at the anus. This 

 skeleton is then measured with a metric scale and map measure, 

 and the percentages divided out with the aid of a slide rule. 



IOTA, Cobb, 1913. 



Fig. 1, Plate II. 



57 



14. 21. 25. -85 Q2. 



1. Iota octangulare, n.sp. .4 mm. 



II. 12. 12. 9. 6. 



Along the longitudinal fields the striae are so modified as to give the 

 worm somewhat the appearance of being covered by eight rows of relatively 

 large scales arranged in pairs. Six small, simple, flattish lips surround the 

 vestibule. The lips are supplied with six small, innervated papillae. These 

 lie in the midst of a plate-shaped disk, the first annule. There are no recog- 

 nized traces of amphids, but the recessive nature of the second annule is 

 suggestive, and it is possible that this peculiarity of the second annule is in 

 some way connected with the amphids. There are no eye-spots. The narrow 

 vestibule leads to the equally narrow pharynx, which consists essentially of 

 a muscular tube closely surrounding the spear. This latter is of relatively 

 very large size, and strictly Tylenchoid in structure. Its length is about 

 equivalent to the first twelve annules of the cuticle. It is divisible into two 

 parts : a long cylindrical hollow shaft tapering to a point near its apex, and 

 having a length about equivalent to the first nine annules ; behind this shaft 

 a basal portion or "hilt," which in its distal part has a structure like that 

 of the shaft, but with a slightly greater diameter. This hilt terminates in a 

 threefold, flattish bulb about one-fourth as wide as the corresponding por- 

 tion of the neck. The lumen of the spear is continuous with that of the 

 oesophagus. This latter consists mainly of a narrow, chitinous tube, which 

 is usually somewhat coiled when the spear is at rest. That portion of the 

 oesophagus containing the hilt of the spear and the coiled oesophageal tube 

 just mentioned constitutes a somewhat obscure elongated "bulb." This bulb, 

 however, is not the morphological equivalent of the bulb usually seen in the 

 oesophagus of Tylenchus and Aphelenchus, as it has no radial muscles, and 

 contains no valvular apparatus. The remaining short portion of the oesopha- 

 gus is tubular and narrow, though it swells slightly at the terminus, where it is 

 about one-eighth to one-ninth as wide as the base of the neck. The ex- 

 cretory pore empties through the exterior margin of the nineteenth annule, 

 or thereabouts. It may be distinctly seen when the worm is viewed from 

 the ventral side, and less distinctly seen in profile. 



Habitat: Dismal Swamp, Va. Flemming solution to glycerine. 



