606 CLARK : NEW GENERA OF CRINOIDS 



Oceanometra, new genus 



Genotype. — Thalassometra giqantea A. H. Clark, 19 33. 



Diagnosis. — A genus of Thalassometrinae (Thalassometridae) in 

 which the dorsal surface of the ossicles of the division series and of the 

 arm bases is covered with numerous prominent spines, which become 

 stouter and more prominent on the proximal and distal borders; there 

 are from 15 to 28 arms; the IIBr series are all, or mostly, 4(3+4); the 

 ossicles of the division series and first four brachials are strongly and 

 evenly rounded dorsally, appearing' relatively narrow; one or both of 

 the elements of each of the pairs of ossicles in the division series, and 

 of the first brachial pair, bears a more or less prominent median keel; 

 the distal borders of the brachials are evenly rounded and very spinous ; 

 the centrodorsal is large, more or less conical, the cirrus sockets arranged 

 in ten columns, two in each radial area; the cirri are of variable length, 

 composed of from 55 to 79 segments. 



Range. — Moluccas to the Philippine and Hawaiian Islands. 



Bathy metrical Range. — From 54 to 858 meters. 



Included Species. — Oceanometra gigantea (A. H. Clark), Oceanometra 

 magna (A. H. Clark), and Oceanometra annandalei (A. H. Clark). 



Crossometra, new genus 



Genotype.- — Pachylometra investigatoris A. H. Clark, 1909. 



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

 more or less conical, with the cirrus sockets arranged in ten definite col- 

 umns, two in each radial area; the cirri are XX-XL, 19-23, stout; 

 there are from 26 to 33 arms 125 mm. to 150 mm. long; the IIBr series 

 are 4(3+4); the IIIBr series are 2(1+2), or 2, internally developed in 

 1-2-2-1 order; IVBr series, if present, resemble the IIIBr series; the 

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

 and sharply flattened against their neighbors, evenly rounded dorsally, 

 with the dorsal surface usually more or less uneven; the brachials are 

 evenly rounded dorsally; the oral pinnules are more slender than those 

 succeeding, though not appreciably longer; the genital pinnules are 

 only slightly expanded, the expansion involving a considerable number 

 of segments and dying away gradually distally. 



Range. — Kei Islands to the Malay Archipelago, the Philippine Islands, 

 and southern Japan. 



Bathy metrical Range. — From 54 to 403 meters. 



Included Species. — Crossometra investigatoris (A. H. Clark), Crosso- 

 metra helius (A. H. Clark), and Crossometra septentrionalis (A. H. Clark). 



Perissometra, new genus 



Genotype. — Antedon flexilis P. H. Carpenter, 18S3. 



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

 more or less conical, with the cirrus sockets arranged in ten definite 

 columns, two in each radial area; the cirri are usually large and stout, 



