182 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



Himerometrinae A. H. CLARK, Proc. Biol. Soc. Washington, vol. 22, 1909, p. 175 (includes Amphi- 

 melra, Himerometra, Craspedometra, and Heterometra) ; Mem. Australian Mus., vol. 4, 1911, 

 p. 728 (raised to family rank), p. 730 (in key, through inadvertence); Journ. Washington Acad. 

 Sci., vol. 5, 1915, pp. 126-134 (bathymetrical range; phylogenetical and palaeontological 

 significance) . 



Himerometres A. H. CLARK, Bull. Mus. Hist. Nat., Paris, No. 4, 1911, p. 250. 



Himorometridae A. H. CLARK, Mem. Australian Mus., vol. 4, 1911, p. 728 (typographical error). 



Diagnosis. A family of the superfaruily Mariametrida in which the elements of 

 the IBr series are united by synarthry and the arms are 10 or more in number; if 

 there are more than 10 arms the IIBr series are typically 4(3+4), though in any 

 individual some of these may be replaced by IIBr series of two elements; the brachials 

 are always short and are frequently always in the 10-armed species exceedingly 

 short with almost or quite parallel ends. The persiome of the disk is usually naked, 

 rarely bearing small scattered concretions, which are especially evident in the anal 

 area (see Part 2, p. 228). The lateral perisome of the pinnules usually contains simple, 

 forked, or multiradiate spicules, very rarely delicate filmy plates of from 2 to 15 meshes, 

 between which and the edge of the pinnulars are small straight or rarely forked spicules 

 or small rods; but calcareous deposits are frequently wholly absent (see Part 2, pp. 

 239-241). 



Geographical range. From southern Japan southward to the Philippines, Tonga 

 and Fiji, Port Molle, Queensland, and to between Fremantle and Geraldton, Western 

 Australia, and westward to east Africa, from the Red Sea southward to Zanzibar and 

 Bagamoyo. 



Bathymetrical range. From the intertidal zone down to 111 (?1S3) meters. 



Remarks. The 41 forms included in the family Himerometridae fall into five 

 genera Himerometra, Craspedometra, Homalometra, Heterometra, and Amphimetra. 

 Amphimetra is rather sharply differentiated from the other four, which together form 

 a closely knit unit. 



The six species of Himerometra are easily distinguished by their narrow and well- 

 separated division series combined with the very short brachials and the much en- 

 larged proximal pinnules, which decrease in size from the lowest outward. But in 

 Himerometra bartschi and in H. persica the proximal pinnules are no stouter than they 

 are in many species of Heterometra and, as in the latter, have the lower segments 

 strongly carinate, while the lowest is sometimes shorter than the next. Also in 

 Heterometra variipinna P 2 , though by no means greatly enlarged, is of quite the same 

 type as the enlarged proximal pinnules in Himerometra magnipinna and in H. sol. 

 Thus Himerometra shows a very close approach to two apparently different genetic 

 lines within the genus Heterometra, although the two genera seem not actually to 

 intergrade. 



An interesting feature of the species of Himerometra is that typically the two 

 outer IIIBr series on each ray are 4(3+4) and the two inner are 2, though this arrange- 

 ment is by no means invariable. This distribution of IIIBr series of 4(3+4) and of 

 2 is not confined to Himerometra, for it occurs also in Craspedometra and is frequently 

 more or less strongly evident in the large species of Zygometra (microdiscus and 

 elegans) and in Heterometra philiberti. 



Although when typically developed its appearance is very distinctive, the single 

 species of Craspedometra is very closely allied with certain species of Heterometra. 



