A MONOGRAPH OF THE EXISTING CRINOIDS 93 



3+4, again from between brachials 23+24 to between brachials 26+27, and from 

 between brachials 42+43 to between brachials 43+44, and distally at intervals of 

 from 11 to 13 muscular articulations. The earlier pinnules are exceedingly long in 

 the adult, with very stout and slightly keeled basal segments. P 2 , which is a good 

 deal longer than P b has as many as 50 segments and is rather fine at its free end. 

 The more distal segments are provided with a spine or tuft of spines. The disk, 

 which has rounded incisions, is about 12 mm. in diameter. The disk, and the arms 

 as far as their last division, are largely washed with purple. The middle line of the 

 arms is lighter, but patches or spots of purple are to be found at the sides. The 

 ventral surface is a little lighter on the disk than on the arms, where it is almost 

 black. 



Bell figured this specimen in dorsal view. There are 89 arms, and all the division 

 series beyond the IBr series appear to be 4(3+4). The division series of three 

 ossicles with "the axillary not a syzygy" mentioned by Professor Bell are undoubtedly 

 4(3+4) series in which the syzygy between the two outer elements was overlooked. 

 Bell figured a cirrus with 59 segments of which the longest are at least half again as 

 broad as long. His figure of the ventral surface, which is to a certain extent schematic, 

 shows a disk in process of regeneration. Bell did not mention the syzygial union of 

 the elements of the IBr series, which he could scarcely have suspected unless one of 

 them had been broken. But his figure shows the extremely short IBr] with a straight 

 distal edge which we have since learned to associate with such a union. 



I have examined Bell's type in the British Museum. The disk is in the early 

 stages of regeneration. The enormously long proximal pinnules, which recall those 

 of such species of Himerometra as H. bartschi, and the very long cirri, which are 40-45 

 mm. in length, are the characteristic features of the species. 



The specimen recorded by Dr. H. L. Clark from off Port Curtis is small, with 

 only 22 arms. Of the eight IIBr series present, seven are 4(3+4) and one is 2. 

 There are four IIIBr series, all 4(3+4). The centrodorsal is low and conical. 

 The cirri are XXV-XXX, 40+. P 2 has 27 segments and is relatively large but 

 less than 20 mm. long. The color, dry, is a uniformly pale brown. 



Abnormal specimens. — In the specimen from South Passage, Shark Bay, one 

 IIBr 2 in a IIBr 4(3+4) series bears, instead of a pinnule, a slightly undersized arm 

 the first division series of which consists of five ossicles, all apparently united by 

 synarthry, and none bearing pinnules. This division series carries two IVBr series, 

 both of which are 4(3+4). The arms have a knotty and irregular appearance, 

 probably due to parasitization. 



In an example with about 80 arms from Siboga station 273 one of the division 

 series is 6(3+4). 



Remarks.— Zygometra microdiscus and Z. elegans are very much alike, and 

 whether they should be regarded as two species or as merely two incompletely differ- 

 entiated forms of the same species is more or less a matter of personal opinion. The 

 relation between them is of much the same order as the relation between Comatula 

 Solaris and C. cratera, between Comatula pectinata and C. purpurea, or between 

 Comanthus timorensis and C. parvicirra. While most specimens may at once be 

 referred either to one or to the other, some are undeniably intermediate and would 

 fit equally well in either. 



