284 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



HETEROMETRA ASTY AN A X. up- nov. 



PLATE 34, FIGURES 152-156 



Diagnostic features. The cirri taper conspicuously distally so that the terminal 

 third or fourth is only about half as broad in lateral view as the proximal portion; the 

 cirri are almost smooth, the last 10-15 segments bearing only slight and inconspicuous 

 dorsal tubercles; the distal cirrus segments are always longer than broad, varying 

 from slightly longer than broad to twice as long as broad ; and the cirri are long, reach- 

 ing rather more than one-fourth the arm length. 



The cirri are 30-33 mm. long, with 37-39 segments. The 19 arms are 120 mm. 

 long. 



Description. The centrodorsal is discoidal, rather thin, with the broad dorsal 

 pole, which is 5 mm. in diameter, almost flat. The cirri are arranged in a single 

 slightly irregular marginal row. 



The cirri are XXVII, 37-39, from 30 to 33 mm. long; they are moderately stout 

 at the base and taper slowly distally so that the terminal third or fourth is only about 

 half as broad in lateral view as the proximal portion. The first segment is about 

 twice as broad as long, and those following slowly increase in length, becoming about 

 as long as broad on the twelfth and from half again to twice as long as broad on the 

 last three or four, on which the cirrus usually tapers with increased rapidity; in some 

 cases these last segments taper more slowly, and they may be scarcely longer than 

 broad. The last 10 to 15 segments bear a subterminal dorsal tubercle, which is 

 scarcely perceptible except on the last five or six. The opposing spine is well de- 

 veloped, slender, and directed obliquely forward. The terminal claw is nearly half 

 again as long as the penultimate segment and is slender and moderately curved. 



The radials are entirely concealed. The lBr l are concealed in the median line 

 but are visible as long narrow triangles extending inward so that their apices are more 

 or less near the midradial line. The IBr 2 (axillaries) are low triangular, three to four 

 times as broad as long, with the lateral angles truncated and thus forming short 

 straight sides which are somewhat more than half as long as the narrow lateral bases 

 of the triangles representing the IBrj. The elements of the IBr series and the first 

 two brachials are in close lateral contact and are sharply flattened laterally. The 

 IIBr series are 4(3+4) and the IIIBr series are 2; there are in the type specimen 

 five IIBr and four IIIBr series, making 19 arms in all. The 19 arms are 120 mm. 

 long. The brachials beyond the proximal quarter of the arms are exceedingly short 

 and almost oblong, as in the species of Himerometra. 



P, is 11-13 mm. long and composed of 17-20 segments. The pinnule is rather 

 stout proximally but tapers rapidly at the end of the proximal half and is flagellate 

 in the distal half. A rather prominent ridge runs the entire length of the pinnule on 

 the outer side, and the second-seventh or -eighth segments are provided with strong cari- 

 nate processes having the distal edge straight and parallel to the axis of the pinnule, 

 which make the pinnule appear disproportionately broad basally. The earlier seg- 

 ments are much broader than long, those succeeding becoming about as long as broad 

 on the ninth or tenth and half again as long as broad terminally. P 2 is 16 mm. 

 long, with 26 segments, of which the earlier are about twice as broad as long, those 

 following becoming as long as broad on the eleventh or twelfth, and one-third again 



