A MONOGRAPH OF THE EXISTING CRENOIDS 197 



In 1933 when describing Crinometra transversa from St. Helena Professor Gisldn 

 wrote that when I established the genus Crinometra I distinguished it from the related 

 genus Pachylometra by the very long proximal pinnules, which should be very strongly 

 carinate, and by the proportionately short middle and distal pinnules, which were said 

 to be not quite half as long as Pi. The genital pinnules should be more abruptly 

 expanded than those of Pachylometra. Besides, there should appear in Crinometra 

 overlapping brachials and usually tuberculation of the basal portions of the arms. He 

 said that in 1918 I considered the difference in length between the proximal and middle 

 pinnules, together with the proximal carination of the former, the chief distinguishing 

 feature between Crinometra and the remaining genera of the Charitometridae. He 

 said that in fact the overlapping of the brachials, the expansion of the pinnules, and 

 the tuberculation of the arm bases are so variable or indefinite characters within 

 Crinometra that they certainly cannot be used for generic characterization. He 

 remarked that the question is whether the character of the middle pinnules, being not 

 quite half so long as Pi, may be used as a distinguishing mark for Crinometra. When 

 studying Hartlaub's treatise on the varieties of Crinometra hrevipinna (1912) he found 

 the following statements. In var. elegans Pi is 10-12 mm. long, and the middle pinnules 

 are 7 mm. long; in var. diadema F t is 8 mm. long, and the middle pinnules are 5 mm. 

 long. He said he had found the same proportions in a specimen of Crinometra insculpta 

 borrowed from the Copenhagen Museum that had been identified by me. He noted that, 

 on the other hand, short middle pinnules may occur in species of Charitometridae that 

 do not fall in Crinometra, as for instance in Perissometra aranea, P. carinata, and 

 Monachometra mortenseni. He remarked it is clear that this feature cannot be used 

 alone for distinguishing Crinometra. But Perissometra aranea, P. carinata, and 

 Monachometra mortenseni belong not to the Charitometridae but to the Thalas- 

 sometridae, all three being synonyms of Parametra orion (see page 72). Gislen wrote 

 it might be asked whether the feature of the long proximal pinnules may not be used 

 together with other distinguishing characters. He said that the carination of the 

 proximal pinnules may be a rather good character, but in some forms referred to this 

 genus it is poorly developed and very insignificant, for instance in granulifera. The 

 tuberculation in some forms is very characteristic and apparent, but is lacking in others. 

 He said that therefore either some forms with smooth arm bases should be excluded 

 from the genus, as C. pulchra, or this feature should not be used as a generic character. 

 He regarded the tuberculation of the arm bases as of small systematic significance. 

 He said that the large number of segments in the proximal pinnules, 20-40, as compared 

 with those of the middle pinnules, 10-15, may be generically important, but similar 

 conditions seem to occur also in some Pachylometras and Perissometras. But in these 

 the length of the middle pinnules does not seem to decrease. In this connection he 

 said it is to be regretted that our knowledge of the proportions of the proximal pinnules 

 is very scanty, especially as regards the more recently described species. 



Since Crinometra transversa, as well as some of the forms of Crinometra previously 

 known, cannot be separated as a group of species which can possibly be distinguished 

 from other Charitometridae, he said that either Crinometra must be given up or it must 

 be provided with an emended diagnosis. The facts seem to speak in favor of the 

 latter solution, and it may be possible to distinguish the genus in the following manner: 

 Crinometra is a genus of the Charitometridae in which the centrodorsal is a thick disk; 



