A MONOGRAPH OF THE EXISTING CRINOIDS 315 



2-3 mm. long with 8 or 9 segments, of which the two basal are broad and short and the 

 others elongate. As in the preceding specimen, it represents the form typical for the 

 middle of the arm. 



The fourth specimen from Blake station 232 is larger than the type specimen, having 

 the arms with an estimated length of 45 mm. Hartlaub says it is rather different from 

 the preceding specimens, and it is doubtful whether it belongs to the same species. 

 Regenerating arms occur on each of the five postradial series. The absence of all 

 ornamentation on the division series is striking. The radials and the elements of the 

 IBr series are smooth; at the most a suggestion of a production of the proximal border 

 of the IBr 2 (axillary) may be noted. The radials are visible, somewhat overlapped by 

 the produced proximal edge of the IBr^ The IBr 2 (axillaries) have a proximally directed 

 posterior process. Subradial clefts occur between the conspicuous interradial processes 

 of the centrodorsal. The IBri and following ossicles have sharply flattened sides. 



The number of arms originally possessed by this specimen cannot now be determined. 

 There are only two of the original arms arising from a IIBr axillary. In one of these the 

 first syzygy is between brachials 3+4, the second is between brachials 19+20, and the 

 third is between brachials 27 + 28; in the other the syzygies are between brachials 5 + 6, 

 18+19, and 26+27. In addition to this IIBr 2 series, there is another similar one, and 

 also one IIBr 4(3+4) series. There are two IIBr 1 series, and one IIBr 2(1+2) series. 



PI is 6 mm. long with 12 segments, all of the same length except the first which is 

 shorter. The pinnules in the middle of the two arms originally present are composed of 

 7 or 8 stout segments; characteristic of these pinnules is the fact that from the third to 

 the penultimate segment they are of approximately the same width, only the terminal 

 segment tapering. The two basal segments are short and moderately broad, all the 

 others elongate. 



A medium sized specimen from Blake station 269, according to Hartlaub, is better 

 preserved and therefore permits a better comparison with the type specimen. It is 

 larger than those previously noticed, with an arm length of about 55 mm. It is note- 

 worthy that on the centrodorsal, which is more flattened than that of the type specimen, 

 the bare dorsal pole is studded with a strongly developed tubercular efflorescence. 

 Smaller tubercles are found on the sides between the cirrus sockets and also on the not 

 especially well developed interradial processes. An opposing spine is developed, as in 

 the first specimen from Blake station 232. In contrast to the type specimen, the 

 radials are scarcely visible. The IBi'i are rather flat, with a well developed median 

 tubercle; small blunt tubercles also occur on the dorsal surface and on the distal 

 edge; the lateral borders are dentate and irregular, as in the type specimen. The 

 ornamentation of its proximal border is more developed than in the type specimen 

 everted and winglike, and also pleated. The IBr 2 (axillaries), which are more rhombic 

 than pentagonal, have a broad median crest; their lateral borders show here and there a 

 typical dentation; the proximal and distal edges are essentially like those of the IBri. 

 As a rule the IIBr series are 2, but one IIBr 4 series is present which all indications 

 suggest owes its origin to regeneration. The elements of the IIBr series have everted 

 proximal borders and often typically dentate lateral edges, as well as a conspicuous 

 median elevation; the axillary is approximately rhombic. The IIBr series and first two 

 brachials have sharply flattened lateral borders. 



