A MONOGRAPH OF THE EXISTING CRINOIDS 195 



6-7 mm. long with 15-18 segments, and the genital pinnules are mostly 5-6 mm. long 

 with 9-14 segments; these proportions are very different from those of the pinnules of 

 either angusticalyx or inaequalis, and agree with those of other forms in the genus 

 Crinometra. 



In 1916 I established five new genera (see Part 3, page 58) as follows: Crossometra 

 (genotype Pachylometra septentrionalis) with the cirri arranged in 10 columns on the cen- 

 trodorsal and 26-33 arms; Perissometra (genotype Antedon flexilis) with the cirri 

 arranged in 10 columns on the centrodorsal and 10-20 arms; Monachometra (genotype 

 Pachylometra Jragilis) with the cirri arranged in 15 columns on the centrodorsal, all 

 the division series 2, and the division series and first two brachials rising rather sharply 

 to a blunt keel; Calyptometra (genotype Charitometra lateralis) with the lateral borders 

 of the elements of the division series and first four brachials strongly everted and with 

 a blunt median keel, the proximal pinnules somewhat longer and more slender than their 

 successors, and 10, rarely 11 arms; and Chondrometra (genotype Chlorometra robusta) 

 with the arms in their outer portion as well as the IBr series and arm bases strongly 

 compressed laterally and rising dorsally into a rooflike keel, with 10 arms, with the cirri 

 in 5 or 10 columns, and with the proximal pinnules about as long as those succeeding. 



In my memoir on the unstalked crinoids of the Siboga Expedition published in 1918 

 I recognized the genera Crinometra, Strotometra, Poecilometra, Charitometra, Chondro- 

 metra, Glyptometra, Crossometra, Perissometra, Monachometra, Pachylometra, Calypto- 

 metra, and Chloromeira. A key to these was given, using the characters given above. 



In his paper on the crinoids collected by Dr. Th. Mortensen in Japan Prof. Torsten 

 Gislen pointed out some inconsistences in my classification. He said it seemed to him 

 very doubtful whether Glyptometra and Perissometra can be maintained as sharply 

 differentiated genera. He noted that as at first diagnosed Glyptometra included some 

 species now referred to Perissometra, a later genus. He remarked that the chief 

 difference between Perissometra and Glyptometra is said to be that the former has on the 

 brachials "a blunt median carination . . . never a low sharp median keel . . . 

 proximal and distal borders of the ossicles of the division series and the lower brachials 

 never everted and standing up at right angles to the general surface of the segments." 

 But he noted that I said Perissometra patida has the "ossicles of the division series and 

 brachials each with a broad low inconspicuous keel which persists to the ends of the 

 arms; distal edges of the discoidal brachials beyond the second prominently and abruptly 

 everted, of the more distal triangular brachials produced and overlapping"; and I also 

 said of P. lata that "the median portion of the ossicles of the IBr series and first two 

 brachials is abruptly raised into an irregular rounded tubercle . . . the proximal 

 and distal borders are more or less irregularly crenulate." The difference in the orna- 

 mentation between Glyptometra as typified by G. tubejrosa and Perissometra as represented 

 by P. patula and P. lata is really strongly marked, though it was perhaps poorly de- 

 scribed. Nevertheless, his point is well taken, and the difference in ornamentation 

 affords no good grounds for generic separation. He quite rightly remarked that the 

 limit between the two genera is obscure, but suggested that perhaps one should, how- 

 ever, be able to retain the two genera in a somewhat altered sense ; G. tuberosa is said to 

 have the cirrus segments provided with a dorsal keel, while on the other hand the species 

 of Perissometra usually have no dorsal spine. With such a limitation, he said, tuberosa 



