CLARK : NEW GENERA OF CRINOIDS 607 



XX-L (usually XX-XXX), 15-31; the arms are from 10 to 20 in num- 

 ber, from 75 mm. to 250 mm. (rarely less than 150 mm.) in length; the 

 IIBr series, when present, are 4(3+4) or, less commonly, 2; the ossicles 

 of the division series and the lower brachials are in close apposition and 

 are sharply flattened against their neighbors; their dorsal surface is 

 smooth or coarsely rugose, raised more or less sharply into a broad or 

 narrow regular or irregular median tubercle, which may be longitudi- 

 nally elongate; the division series usually make a relatively small angle 

 with the dorsoventral axis, so that the lower part of the animal is rela- 

 tively narrow; the brachials are evenly rounded dorsally, and the more 

 proximal may bear a small rounded dorsal tubercle; the oral pinnules, 

 though more slender than those succeeding, are not appreciably longer; 

 the genital pinnules are only slightly expanded, the expansion always 

 involving a number of segments and gradually tapering away distally. 



Range. — Laccadive and Andaman Islands to Timor and the Kei 

 Islands, and northward to the Philippines and southern Japan. 



Bathymetrical Range. — From 73 to 1289 meters. 



Included Species. — Perissometra angusticalyx (P. H. Carpenter), Peris- 

 sometra patula (P. H. Carpenter), Perissometra robusta (P. H. Carpenter), 

 Perissometra selene (A. H. Clark), Perissometra gorgonia (A. H. Clark), 

 Perissometra timorensis (A. H. Clark), Perissometra crassa (A. H. Clark), 

 Perissometra lata (A. H. Clark), Perissometra flexilis (P. H. Carpenter), 

 Perissometra invenusta (A. H. Clark), and Perissometra macilenta (A. H. 

 Clark). 



Monachometra, new genus 



Genotype. — Pachijlometra frag His A. H. Clark, 1912. 



Diagnosis. — A genus of Charitometridae in which the centrodorsal is 

 thick-discoidal or more or less columnar, with the cirrus sockets ar- 

 ranged in fifteen crowded columns; the cirri are XXX, 19; ths arms are 

 from 15 to 19 in number, 145 mm. long; all the division series are 2; 

 the ossicles of the division series and the first two brachials are sharply 

 flattened laterally, with the dorsal surface rising rather sharply into a 

 blunt keel; the IBri are produced inwardly, so that their inner apices 

 nearly meet in the center of the calyx; the visceral mass rests on the 

 ossicles of the IIBr series and first two brachials, and on the sharply 

 flattened and almost horiz ntal inner face of the IBr 2 (axillary); the 

 synarthrial articulations (between the elements of the division series 

 and between the first two brachials) are extraordinarily brittle; the 

 brachials have a faint and obscure median carination; the oral pinnules 

 are of approximately the same length as those succeeding, though more 

 slender; the genital pinnules are. rather stout, but without a localized 

 expansion. 



Range. — Philippine Islands and the Moluccas. 



Bathymetrical Range. — From 118 to 243 meters. 



Included Species. — Monachomstra fragilis (A. H. Clark). 



