416 BULLETIN 8 2, UNITED STATES NATIONAL MUSEUM 



Thermal range.— From 15.89° to 24.28° C. 



Remarks. — The two genera included in this family are closely related, but on the 

 basis of the somewhat scanty information available they appear to be distinct. In 

 the characters of the centrodorsal and cirri Pterometra magnipeda and Pt. pulcherrima 

 resemble the species of Asterometra, but in their other characters they are more closely 

 related to the other species of Pterometra. 



History. — The family Asterometridae was established by Prof. Torsten Gisl^n in 

 1924. In his superfamily Thalassometrida (= Tropiometrida) Professor Gisl6n 

 recognized two subtribes, (a) Thalassometrida with no radial pits in the centrodorsal 

 and the articular facets of the synarthries narrow and occupying only a part of the 

 synarthrial face, including the families Thalassometridae, Charitometridae, and 

 Calometridac; and (b) Notocrinida with deep radial pits and the articular facets 

 occupying almost the whole of the synarthrial face. The Notocrinida he divided into 

 two sections, (1) Notocrinida with the side- and covering-plates moderate, the bra- 

 chials and pinnule segments rounded, and the genital glands in the arms, including the 

 family Notocrinidae ; and (2) Asterometridae, new family (including Asterometra and 

 Pterometra), with the side- and covering-plates well developed, the brachials and pin- 

 nule segments prismatic-triangular, and the genital glands in the pinnules. 



It seems to me that the family Notocrinidae in which all the pinnules, includmg 

 the oral, are rounded, and the side- and covering-plates are rudimentary finds its 

 logical position in the Macrophreata, and is quite out of place m the Tropiometrida. 

 On the other hand, the species of Asterometridae in all their characters except the 

 deep radial pits are in rather close agreement with the species of Thalassometridae, 

 and in still closer agreement with the species of Ptilometridae with which I formerly 

 united them in the subfamily Ptilometrinae of the family Thalassometridae. But as 

 they form a very distinctive, though small, group there are certain advantages in 

 following the lead of my friend Professor Gisl^n and recognizing them as representing 

 a distinct family. 



KEY TO THE GENERA OF THE FAMILY ASTEROMETRIDAE 



a'. Arms 20-30 in number; pinnules in the proximal third of the arms as long as, or even longer than, 

 those in the distal half, composed of segments many or most of which are constricted cen- 

 trally with produced and spinous distal ends; longer proximal cirrus segments usually more or 

 less constricted centrally with prominent distal ends the ventral border of which usually over- 

 laps more or less the base of the segments succeeding and may be produced into a long ventral 

 spine (from the Kei Islands and eastern Java northwestward to the Gulf of Martaban and 

 northward to Cochin China, the Philippines, and the Bonin Islands; 5-106 [?183] meters). 



Pterometra (p. 416). 



a'. Arms 10-16 (rarely over 13) in number; pinnules in the proximal third of the arm much shorter 

 than those in the distal half, composed of segments which, except occasionally at the extreme 

 tip, do not have overlapping and spinous distal ends; proximal cirrus segments with no cen- 

 tral constriction or production of the distal edge (from the Kei Islands and the Sahul Bank 

 westward to Bali and northward to the Bonin Islands and southwestern Japan; 73 [?72I = 256 

 meters) Asterometra (p. 432.) 



Genus PTEROMETRA A. H. Clark 



Ptilometra (part) A. H. Clark, Smithsonian Misc. Coll., vol. 52, pt. 2, 1908, p. 224. 

 Asterortietra (part) A. H. Clark, Proc. U. S. Nat. Mus., vol. 39, 1911, p. 546. 



Pterometra A. H. Clark, Proc. Biol. Soc. Washington, vol. 22, 1909, p. 177 (diagnosis; genotype 

 Ptilometra trichopnda A. H. Clark, 1908; referred to the Tropiometridae) ; Via. Medd. Naturh. 



