A MONOGRAPH OF THE EXISTING CRINOIDS 283 



viewed laterally, until the last six or eight segments, on which they taper to the tip; 

 or they may taper very gradually in the distal half, third, or fourth; sometimes they 

 broaden almost imperceptibly from about the eighth segment, slowly tapering in the 

 distal fourth. The antepenultimate segment is small, wedge-shaped, slightly broader 

 than the ventral length. The terminal claw is about half again as long as the ante- 

 penultimate segment, and is rather stout and moderately and evenly curved. 



The radials are just visible beyond the rim of the centrodorsal, or they are 

 concealed in the midradial line, their anterolateral angles being visible in the inter- 

 radial angles of the calyx where the anterolateral angles of adjacent radials form 

 together a low triangle of which the very sharp lateral angles almost or quite meet in 

 the midradial line. The IBr t are exceedingly short, from six to eight times as broad 

 as long, and may be partially concealed by the centrodorsal. They are in lateral 

 contact. Their proximal and distal borders are slightly prominent. The IBr 2 (axil- 

 lari'es) are triangular, twice as broad as long, with the distal sides slightly or moderately 

 concave. The proximal half of the midradial line of the axillaries and the adjacent 

 portion of the IBr] are raised into a small, low, and very broadly rounded, often obscure, 

 synarthrial tubercle. 



The 10 arms are about 180 mm. long. The first two brachials are markedly 

 larger than those succeeding, this being especially true of the second. The first brachials 

 are wedge-shaped, half again as long exteriorly as interiorly, and more or less com- 

 pletely united interiorly. The second brachials are triangular, with the outer edge 

 more or less longer than the outer edge of the first brachials, and the inner edge 

 reduced to a point. The first syzygial pair (composed of brachials 3+4) is wedge- 

 shaped, slightly more than twice as broad as the median length; the hypozygal (third 

 brachial) is very short and band-like, with the proximal and distal borders parallel. 

 The inner edge of the epizygal (fourth brachial) is as long as, or slightly longer than, 

 the inner edge of the hypozygal, but the outer edge is reduced to a point. The next 

 four brachials are oblong, about four times as broad as long. After the second syzygy 

 the brachials are triangular, short, about four times as broad as the median length, 

 with a small rounded triangular projection in the mid-dorsal line and a prominent 

 angle deeply incising the proximal border of the succeeding brachial halfway between 

 the mid-dorsal line and the base of the pinnule. After about the thirtieth the brachials 

 become wedge-shaped again, and after the proximal third of the arm slowly increase 

 in length so that the terminal brachials are longer than broad with slightly oblique 

 ends. The distal ends of the brachials are marked with exceedingly fine longitudinal 

 striations, and the distal edges are very finely spinous. On the distal brachials most 

 of the dorsal surface is marked with fine striations. The first two brachials have a 

 broad but very low and somewhat obscure median carination. On the brachials 

 succeeding this is narrowed, becoming a fine low narrow line with the distal portion 

 somewhat elevated, so that the dorsal profile of the arm is strongly serrate. This 

 carination becomes obscure after the proximal fourth of the arm, and in the outer 

 half of the arm completely disappears, the dorsal profile of the arm becoming entirely 

 smooth. 



Syzygies occur between brachials 3+4, 9+10, and 14+15, and distally at inter- 

 vals of from 4 to 9 (usually 6) muscular articulations. 



