328 



BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



( J . Terminal segment of abdomen not armed with a long median terminal spine. 

 </. Four anterior segments of thorax with spines or tubercles. Middle surface 

 of abdomen with prominent spiny projections. With conical lateral pro- 

 jections. Epimera pointed Arcturus bajfini ( Sabine) 



d r/ . Four anterior segments of thorax without spines or tubercles. Middle 

 surface of abdomen without any indication of prominent spiny projec- 

 tions. Without conical lateral projections. Epimera less pointed. 



Arcturus baffini var. tuberosus Sars 



ARCTURUS BERINGANUS Benedict. 



Arcturus beringanus BENEDICT, Proc. Biol. Soc. Washington, XII, 1898, pp. 46- 

 47. RICHARDSON, Proc. U. S. Nat. Mus., XXI, 1899, p. 854; Ann. .Mag. 

 Nat. Hist. (7), IV, 1899, p. 275; American Naturalist, XXXIV, 1900, p. 229. 



Localities. Alaska; Bering Sea. 

 Depth. 29-72 fathoms. 



Body narrow, elongate, a little more than seven times longer than 

 wide, 1 mm. : 11 mm., not including the antennae. 



The head is about as wide as long, \\ mm. : li mm. , with the ante- 

 rior margin deeply excavate. The e} 7 es are small, round, composite, 

 and situated at the sides of the head about halfway between the ante- 

 rior and posterior margins. The first pair of antennae 

 have the basal article long and somewhat dilated; the 

 second is longer than the third, and both together are 

 about equal in length to the first; the fourth is a little 

 longer than the first. The first antennae extend to the 

 end of the second article of the peduncle of the second 

 pair of antenna?. The basal article of the second an- 

 tennae is short, and extends as far as the antero-lateral 

 angles of the head, or to the end of the first article of 

 the first pair of antennae; the second article is longer 

 and extends to the end of the first pair of antennae; 

 the third article is twice as long as the second; the 

 fourth is twice as long as the third; the fifth is a little 

 shorter than the fourth. The flagellum is composed of 

 four articles, the last article terminating in a spine. 

 The second antennae are shorter than the body, being 

 only T^ mm. in length. The maxilliped has a palp of 

 five articles. The palp of the mandibles is wanting. 

 The first three segments of the thorax are subequal; the fourth is 

 twice as long as any of the preceding segments; the fifth is half as 

 long as the fourth; the sixth is as long as the fifth; the seventh is a 

 little shorter than the sixth. The first segment has the lateral parts 

 somewhat expanded to surround the posterior portion of the head. 

 The epimera of the second, third, and fourth segments are distinctly 

 separated from the segments, are small and narrow, not visible from 

 a dorsal view, and occupy the antero-lateral angles of the segments. 

 The epimera of the last three segments are also distinctly separated 



FIG. 359. ARCTU- 

 EUS BERINGANUS 

 (AFTER BENE- 

 DICT), x 2i. 



