FREE-LIVING NEMATODES 31 



THORACOSTOMA, Marion, 1870 



25. Thoracostoma polare, n. sp. The thick yellow cuticle is traversed by mi- 

 nute, transverse striae difficult of resolution, and in its deeper layers, at least 



near the head, by fine ^_ J V ^ 38 



oblique striae crossing each lfc -1^ V\ : - - 8 - 14< t<5 ' "' ? 

 other at an angle of about pc .--/t--r*f' ^ \ ' 4 1- " 3 1-5 ' 8 

 forty-five degrees. Subce- \*-'ffij$M\ .2 4.9 12. _ M - 69 99.4 



phahc setae, like the ce- \^r^\\\j/^ \ .4 i'g i';' 3 ' i'T '^ i9.a 



phalic in form and size, oc- 

 cur in groups of three or four together, near the border of the "cuirasse," and a 

 little farther back. Similar cervical setae occur on the anterior part of the neck 

 singly and separated by a distance one-fourth to one-third as great as the diame- 

 ter of the neck measured at the middle. The remaining cervical setae as well as 

 the somatic setae are reduced to papillae. All these setae are arranged in more 

 or less irregular lateral and submedian lines. The head is furnished with a chiti- 

 nous, faintly yellowish "cuirasse," extending back to opposite the base of the 

 pharynx, and divided longitudinally into six lobes by as many sutures. Each 

 of these lobes is perforated near the posterior margin by two oblique, irregular 

 locules, each a little more than half as long as the amphids are wide. The three 

 amalgamated lips are nearly obsolete. Six forward pointing, inconspicuous, in- 

 nervated papillae form a single circlet on the front of the head. The simple, 

 rather narrow, more or less irregularly pyramidal, well chitinized pharynx is as 

 long as the head is wide, and is somewhat narrowed posteriorly, where the two 

 ventrally submedian oesophageal glands empty into it. The third oesophageal 

 gland, ventral in position, empties into the lumen of the oesophagus a little more 

 than halfway back to the eye-spots. When shut the pharynx rather closely 

 resembles the lumen of the oesophagus, which possesses a well developed chiti- 

 nous lining. The only armature of the pharynx is the dorsal, labial, two-lobed 

 cordiform piece of chitin just at the mouth opening, arranged much as described 

 by Dr. de Man for Thoracostoma antarcticum, v. Linst. Two faint refractive lines 

 close together lead backward from the posterior part of each amphid. The two 

 rather widely separated eye-spots are located at a distance from the anterior 

 extremity equal to four times the width of the head, and are one-sixth as wide 

 as the corresponding part of the neck, and about as long as wide. These are 

 somewhat heart shaped, and are composed of compactly arranged brownish 

 granules. There are obscure indications of a refractive body, or "lens," in the 

 hollowed out front part of each eye-spot. The conoid oesophagus is about half 

 as wide as the neck, and presents a faint, elongated pharyngeal swelling. The 

 cylindroid cardia is one-fifth to one-fourth as wide as the base of the neck. The 

 thick-walled intestine, separated from the oesophagus by a collum one-third as 

 wide as the base of the neck, becomes at once three-fifths as wide as the body, 

 and is about six cells in girth. The intestinal cells contain numerous uniform, 

 colorless granules. The posterior lip of the anus is slightly elevated. 



The hemispherical-conoid to convex-conoid tail tapers from the anus and 

 ends in a very broad, bluntly rounded terminus. The spinneret is a very slightly 

 depressed pore with a suggestion of yellowish color, arranged a little unsymmetri- 

 cally, so that it empties somewhat toward the ventral side, and not axially. It 



