A MONOGRAPH OF THE EXISTING CRINOIDS 135 



of the arms from the base outward. More frequently specimens are found in which 

 all or some of the arms are uniform in width from the base to the middle, as in the 

 types of pulchella. 



The arms are best preserved in 2 large specimens from Blake station 189. They 

 measure, so far as they are preserved, 100 mm. from the first brachial and the 

 missing tip may be estimated to have measured 15 mm., so that the total length 

 would have been 115 mm. In a specimen from Barbados (or Montserrat) the arms 

 as far as preserved measure 95 mm. and consist of 119 brachials. 



In arms arising from a IBr axillary the first two brachials are short and discoid al 

 and are united by synarthry. Then follows the first syzygial pair, which is approxi- 

 mately square, then 3 somewhat shorter approximately oblong brachials; with the 

 seventh, or at the latest with the ninth, the long series of triangular brachials begins 

 which at about the fortieth passes over into short wedge-shaped brachials. The 

 first 2 brachials contrast with those following by their greater breadth, especially if 

 they lie by the side of a IIBr series on the same IBr axillary, in which case they tend 

 to resemble the elements of the IIBr series. The length of the triangular brachials 

 is relatively constant. In the variety planata the series is interrupted by wedge- 

 shaped syzygial pairs. In the form of the brachials, as well as in the mode of union 

 between them the triangular brachials of the pulchella and planata types are similar 

 to those of Leptonemaster venustus. 



The arms arising from a IIBr axillary differ from those arising from a IBr axillary 

 in that the first 2 brachials, which are syzygially united, are not broadened. 



Specimens with entirely smooth arms are rare. As a rule even in the relatively 

 smooth-armed varieties of pulchella and planata there is a certain roughness resulting 

 from a slight overlapping of the distal ends of the brachials. 



In arms arising from a IBr axillary the first syzygy is between brachials 3+4, or 

 rarely between brachials 4 + 5, and the second is sometimes as early as between bra- 

 chials 6 + 7, though as a rule from between brachials 12 + 13 to between brachials 

 22 + 23, most commonly from between brachials 12 + 13 to between brachials 16 + 17. 



In arms arising from a IIBr axillary the first syzygy is between brachials 1+2 

 and the second usually between brachials 3+4, though sometimes between brachials 



4 + 5 or 5 + 6. Occasionally it is omitted, so that the second syzygy occupies the 

 position usually taken by the third. This is the case on several arms of a specimen 

 from Blake station 158 and on 5 arms of a specimen from Blake station 148. Some- 

 times, as in another large specimen from Blake station 158, a syzygy between brachials 



5 + 6 immediately follows one between brachials 3 + 4. The syzygy between brachials 

 1 +2 is rarely absent, but this occurs on one arm of a specimen from Blake station 148. 



The intervals between the following syzygies are very variable. The greatest 

 constancy is found in the variety planata, where the intersyzygial interval is from 

 3 to 6 muscular articulations, usually 4 or 5. The conditions in typical pulchella, on 

 the contrary, are very diverse. In the dark-brown specimens from Blake station 

 45Ag. the intersyzygial interval is not over 5 muscular articulations, most commonly 

 3 or 4. On other specimens the usual number is 5 or 6, while on still others it is 

 8-10, or even 8-13. The intersyzygial interval often decreases distally. 



