Body practically cylindrical throughout the greater portion of its length, tapering in the anterior third of the neck until the lip region is about one-fourth as wide as the neck base.  Cuticle marked by easily visible transverse striae.  Lateral cords about one-fourth the body width, composed of closely packed cellular bodies, each connected with a lateral pore.  Amphids about one-third head width.  Lip region thoroughly amalgamated, set off by deep constriction.  The rounded lips surround a strongly cuticularized basket-like structure with a jagged, denticulated opening in the bottom through which the spear glides.  From this basket-like structure six obscure, cuticularized rods extend back to the spear guiding ring.  Spear small, shorter than the head width, the aperture occupying almost half its length.  The esophagus begins as an elongate swelling about one-third as wide as the neck but almost immediately narrows to a slender non-muscular tube with a prominent lumen which is definitely altered in structure where it joins the lumen of the enlarged portion.  At the junction the esophagus abruptly expands so that the posterior three-fifths of the esophagus is about half as wide as the neck.  Only the dorsal and the two posterior ventrosubmedian gland nuclei were observed.  These two posterior nuclei are widely separated and are located from the base of the esophagus a distance equal to about one and two body widths respectively.  Cardia bluntly conoid, one-fourth as wide as body.  Intestine about eight cells in circumference.  Vulva transverse.  Vagina very small, extending about one-third the distance across the body.  The short ovaries are reflexed about half way back to the vulva.  Average length of eggs twice the body width.  Female rectum and prerectum each somewhat longer than anal body diameter.  Spicula relatively small, arcuate, with slender lateral guiding pieces.  Supplements consisting of the usual adanal pair and, beginning about one body width anterior to these, 15-20 others of which the first two to six are located slightly off the ventral line, forming one to three diagonally-located pairs.  Male prerectum slightly longer than the body width.  Female body tapering from a short distance in front of the anus to the blunt, convex-conoid tail.  Male tail dorsally arcuate to the blunt terminus.

Diagnosis:  Carcharolaimus with the above measurements and general description.  Appears to be most closely related to C. rotundicauda from which it differs in the details of the pharynx and in the longer neck.  Males found in only one of many collections.

Habitat:  A common species from valley, desert and mountain soils of the Great Basin, Western United States.  Also from desert soil, Littlefield, Arizona; Barstow, California; and cultivated fields, Riverside, Azusa and Oxnard, California, U.S.A.
(Description- Thorne, 1939)

DNA Sequences Obtained

Specimen:	Collected:
Ord1	Ord, NE
TXB586	Texas