A MONOGRAPH OF THE EXISTING CRINOIDS 285 



to him necessary, in order to portray the species adequately, to establish a large number 

 of varieties. 



He emphasized the fact that in his attempt to determine the diagnostic characters 

 of the species his account is to be regarded as couched only in general terms and appli- 

 cable to the majority of, but not all, the individuals. 



In his attempt to determine some of the characters of the species Hartlaub said 

 that the centrodorsal is often flat with a prominant incised dorsal pole, which is usualty 

 ornamented. Interradial processes are present, but interradial ridges are rarely 

 developed. 



The number of cirri is very different in the different varieties, ranging between 

 XV and XL. The number of cirrus segments varies from 12 to 20. The antepenulti- 

 mate segment bears an opposing spine. The cirri are relatively short. 



The radials are not visible. The elements of the IBr series are usually flattened 

 dorsally. The IBr axillaries as a rule lack a proximally directed process. The IIBr 

 series are either 2 or 4(3+4). The ossicles from the IBr axillary to the fourth or fifth 

 brachial are in close lateral contact and sharply flattened laterally. The basal orna- 

 mentation, which is always different from the ornamentation of the arms, as well as 

 the darker color, if present, also does not extend beyond the fourth or fifth brachials. 



There is often a striking lateral compression of the arms. In regard to the lower 

 brachials, a dual form is often conspicuously evident; the first few brachials (about 3) 

 are quadrangular, with parallel edges and right angles; these are followed by a few 

 (about 4) bluntly wedge-shaped brachials; then there are a few (usually 2) quadrangular 

 brachials; following these, often quite abruptly, are triangular brachials that persist 

 to the arm tips. Corresponding to the shape of the brachials, the articidations cross 

 the arm either transversely or diagonally. 



The first syzygy is between brachials 1 + 2 or 3 + 4, and there may bo a syzygy 

 in both positions so that an arm begins with two syzygial pairs. The position of the 

 following syzygies is inconstant in the same individual, and in different individuals 

 so very variable that this point must be considered in the accounts of the different 

 varieties. 



The length of P D and of Pi is very variable, according to Hartlaub, the size of the 

 individuals naturally playing a certain part in this. The length of P D varies between 

 8 and 17 mm., that of Pi between 6 and 12 mm. The number of segments in these 

 pinnules is also variable, though in this the size of a given variety seems not to play 

 a significant part. The number of segments in P D varies between 30 and 40, in Pi 

 between 20 and 40; in Pi there are usually 20-30 in the individual varieties. The 

 segments of these pinnules are short, the basal always more or less singly or doubly 

 carinate. Generally speaking, the following pinnules decrease gradually in length 

 and in the number of their segments, m both these features attaining a certain degree 

 of uniformity in the middle of the arms. The pinnules in the middle of the arms are 

 3-7 mm. long with 7-13 segments of which the two first are, as a rule, short and broad 

 and the remainder elongate. Toward the ends of the arms in all tho varieties the length 

 of the pinnules increases. When gonads are developed the few segments covering them 

 (about 3) are broadened. The ambulacral plating is always very prominent and con- 

 sists of side and covering plates. 



The disk is usually flat and is often deeply incised. 



