Chiriscus australis Richardson 1911

“Chiriscus australis, new species.

Body ovate, a little more than twice as long as wide, 8 mm. by 3 ½ mm. Color, in alcohol, light brown, with a small patch of black on either side of the posterior portion of the head and on either side of the antero-lateral parts of the first thoracic segment; there is also a transverse band of black on the termi­nal abdominal segment.

The head is twice as wide as long, 3 mm. by 1 ½ mm., with the anterior margin pro­duced into a conspicuous median point. The head is deeply immersed in the first thoracic segment, but the lateral parts are pro­duced and expanded in wide plates, the margins of which are entire. The eyes have almost disappeared; they are situated some distance from the lateral margin in the posterior half of the head. The first pair of antennae have the basal article large and dilated, with the post-lateral margin produced in a small rounded lobe; the second article is narrow, elongate, about one and a half times the length of the first, and is inserted in the outer lateral margin of the basal article; the third article is about as long as the second; the flagellum is composed of a single large article, about half the length of the third article of the peduncle, and a minute terminal article. The first antennae extend beyond the post-lateral angles of the head by a distance equal to the length of the flagellum; the second antennae are extremely short, extending only to the end of the second article of the peduncle of the first antennae, and are geniculate at the second article; the first article short; the second is twice as long as the first; the third and fourth are short, about equal in length to each other and to the first article, the fourth having the outer lateral margin produced in a large rounded process or lobe; the fifth article is a little longer than the preceding; the flagellum is composed of eleven articles. The sec­ond antennae are almost entirely concealed in a dorsal view by the first antennae.

The first, second, and third segments of the thorax are about equal in length in the median line, being each three-fourths mm. long; the fourth, fifth, and seventh segments are a little shorter, being each about one-half mm. in 1ength; the sixth segment is the longest, being 1 mm. long. Epimera are present on all the segments except the first; they are visible in a dorsal view only on the last three, being wide and occupying the entire lateral margin; in the other three segments they are narrow plates and extend only half of the lateral margin. The thorax tapers toward the posterior extremity, which is narrower than the anterior portion. The seventh segment is abruptly narrower than the sixth segment, and is not wider than the first abdominal segment.

The abdomen is composed of three segments, two short segments anterior to the long terminal segment. The terminal segment is long and narrow, 3 mm. by 1 ½ mm., and tapers to a pointed extremity.

The first pair of legs are strongly prehen­sile, with the propodus large, dilated, and the dactylus long and reflexed. The carpus is produced on the exterior margin in a long spine-like process at the base of the propo­dus. The two following pairs of legs are not prehensile, but are similar to the fourth, fifth, and seventh pairs, with the exception that the basis is more dilated and the carpus produced in a long wide process extending half the length of the propodus. In all five pairs, the last three articles are fringed with long hairs, and there is no dactylus. The sixth pair is much longer than any of the others and has the carpus and propodus elongate. This pair has a small blunt dactylus.

Only one specimen was obtained by the Albatross at station 2764, off Rio de la Plata, Argentina, at a depth of 11 ½ fathoms on sand and broken shells.

Type.—Cat. No. 42092, U.S.N.M.”

(Richardson, Harriet, 1911: 169-171)

Chiriscus australis là một loài chân đều trong họ Chaetiliidae. Loài này được Richardson miêu tả khoa học năm 1911.