A MONOGRAPH OF THE EXISTING CRINOIDS 31 



Comanthus cumingii. Himerometra anceps. 



Comatella nigra. Himerometra milherti. 



Zygometra elegans. Himerometra variipinna. 



Pontiometra andersoni. Himerometra protedus. 



Himerometra persica. Himerometra monacantha. 



Himerometra bengalensis. Cyllometra manca. 



Himerometra quinduplicava. Oligometra pulchella. 

 Thalassometra compressa. 



Another paper published in December is essentially a composite of the paper 

 based upon a review of Bather's description of Ptilocrinus antardicus and that on 

 the ecology of the recent crinoids. 



It had been evident for some time that the status of the families Himerometridae 

 and Thalassometridae was unsatisfactory, and on January 9, 1909, a revision of both 

 these families was published, with keys to all the included genera. 



It was stated that although the new genera described are based upon obvious 

 external characters in order that they may be readily recognized and identified 

 from ordinary museum material, in many cases, as with the larger divisions, the best 

 characters are found in the musculature studied from the point of view of skeletal 

 muscle insertions, and in the internal structure of the centrodorsal. 



The Thalassometridae was found to include two well-defined groups; in one the 

 cirri are short, stout, and smooth, and Pi is slender and composed of very short seg- 

 ments, while in the other the cirri are long, comparatively slender, and spinous, and 

 Pi is stout and composed of enlarged segments. The cirri of the latter morphologi- 

 cally differ from those of the former in the distal addition of numerous segments bearing 

 dorsal spines, and the Une of demarcation between these two types of segments is 

 commonly marked by a so-called "transition segment" representing the penultimate 

 segment in the cirri of the short smooth type. The increased cirrus length is corre- 

 lated, as is commonly the case in the comatuhds, with an increase in the size of the 

 lower pinnules. 



The species of the Himerometridae are distributed among 1 1 genera, of which 7 

 are new; these genera, with the included species, are: 



Pontiometra, including 



Pontiometra andersoni. 



Colohometra, gen. nov. (genotype Antedon perspinosa P. H. Carpenter, 1881), 

 including 



Colohometra perspinosa. Colohometra suavis. 



Cyllometra, including 



Cyllometra alhopurpurea. Cyllometra impinnata. 



Cyllometra anomala. Cyllometra injormis. 



Cyllometra darae. Cyllometra manca. 



Cyllometra tigrina. 



