200 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



The family Charitometridae is closely allied to the family Thalassometridae, but it 

 represents a more generalized type. The cirri are less specialized, lacking the polished 

 spine-bearing segments beyond the transition segment characteristic of the Thalas- 

 sometridae. They may be said to correspond to the cirri of the Thalassometridae as 

 far as the transition segment, for the penultimate segment often has a polished distal 

 end like the transition segment of the Thalassometridae. The oral pinnules of the 

 Charitometridae are usually about as long as the pinnules following, but are more 

 slender and flexible with much more numerous short segments. They are less modified 

 than the elongate and basally stout oral pinnules of the Thalassometridae. In the 

 Charitometridae there are usually two pairs of oral pinnules except in very small species 

 while in the Thalassometridae there is only a single pair except in some large species in 

 which the second pair may be more or less intermediate. Similarly the genital pinnules 

 are more generalized than those of the Thalassometridae, being longer and in most cases 

 more like the distal pinnules. The pinnules in general are not so much stiffened as are 

 those of the Thalassometridae. In the famdy Thalassometridae there is an approach 

 to the Charitometridae in the genus Parametra in which the cirri have only a few seg- 

 ments beyond the transition segment, and Pi is not greatly longer or stouter than the 

 pinnules following. 



The genera of the Charitometridae do not fall into distinctive groups as do those of 

 the Thalassometridae, but the first group in this family, with the arms strongly com- 

 pressed laterally and sharply carinate, finds a parallel in the genus Chondrometra. The 

 genera with the genital pinnules abruptly swollen are not so sharply differentiated from 

 the others as they are in the Thalassometridae. 



The family Charitometridae is less widely distributed than the Thalassometridae, 

 not extending, so far as is now known, to the Aleutian or Galapagos Islands, south- 

 eastern Australia, or the Crozets, nor does it occur in the Atlantic basin except in the 

 Caribbean and at St. Helena. Its bathymetrical and thermal ranges are also con- 

 siderably less. 



History. — The species now included in the family Charitometridae were distributed 

 by Dr. P. H. Carpenter among the Basicurva group, the Acoela group, the Spinifera 

 group, and the Granulifera group. In 1905 Minckert diagnosed the Brevipinna group 

 the type species of which is the same as that of Carpenter's Granulifera group. In 1905 

 Prof. F. Jeffrey Bell described a species of this family, and another of the family Thalas- 

 sometridae, in Carpenter's Savignyi group. 



In 1907 I segregated all the described species now considered as belonging to this 

 family in the genera Chariiometra and Poecilometra (see Part 3, p. 8). In a paper 

 published on April 11, 1908, I distributed the living comatulids among several families, 

 assigning the genera Chariiometra and Poecilometra to the family Thalassometridae. 

 In a paper written considerably in advance of this though not published until May 14 

 (see Part 3, p. 15) the same arrangement is suggested. In 1909 the genera Chariiometra 

 and Poecilometra, together with the new genera Glyptometra, Strotometra, Pachylonutra, 

 Chlorometra, and Crinometra, were segregated as a new subfamily Charitometrinae of 

 the family Thalassometridae (see Part 3, p. 33). In my memoir on the recent crinoids 

 of Australia published in 191 1 the subfamily Charitometrinae was raised to family rank 

 and designated as the family Charitometridae. 



