Illacme plenipes, new species.
Body very slender and flexible, filiform, strongly and evenly convex, moderately pubescent on all of the exposed surfaces; number of segments attaining 192, with a length of 36 mm. and a width of 0.7 mm. in the largest female specimen; other individuals 26 to 29 mm. long, 0.5 to 0.6 mm. wide, with 136 to 152 segments.
Head rather narrowly triangular-cordate, the vertex more densely hirsute, the hairs rather short, the clypeus with longer and sparser hairs, nearly naked above the rather blunt-pointed labium; position of head nearly vertical, not strongly recurved under the body.
Antennae inserted at the sides of the head, moderately hirsute, abruptly capitate-clavate, subgeniculate, the terminal joints carried at the sides of the head, the second and third joints at the lateral margin of the first segment; joints 2 to 4 gradually thicker but much smaller and narrower than joints 5 and 6; joint 2 somewhat longer than joints 3 and 4, which are subequal and nearly as broad as long; joint 5 also about as broad as long, but much thicker than joint 4; joint 6 slightly narrower than joint 5, and distinctly longer, about one and one-half times as long as broad, cylindric-oval, slightly narrowed toward the end; joint 7 projecting as a rather broad frustum about one-sixth of the length of joint 6; olfactory cones not prominent.
First segment with the lateral margins evenly rounded and the anterior margin nearly parallel with the posterior; the surface more even than on other segments, which are abruptly convex behind the transverse constriction.
Penultimate segment without legs, the large pleura meeting in the middle and apparently united, but the sutures indicated by a fine median groove; last segment converging to a broadly rounded apex, not projecting beyond the margins of the valves, scarcely equal to the margin when viewed from the side.
Type.—Cat. No. 976, U.S.N.M.
Numerous specimens were collected by O. F. Cook in San Benito County, Calif., November 27, 1926, a short distance after crossing the divide between Salinas and San Juan Bautista. Only one colony was found, in a small valley of a northern slope wooded with oaks, under a rather large stone. The living animals were nearly white, moved very slowly, and rolled themselves into regular, close spiral coils when disturbed, the coils with three or four turns.
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