186 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



Si&offo-Exped., 1918, p. 72 (in key; range), p. 73 (key to the included species). GisiJaN, Zool. 



Bidrag Uppsala, vol. 9, 1924, p. 35 (brachial homologies) , p. 51 (obliquity of brachials), pp. 92, 99 



(pinnule articulations) . GISL^N, Kungl. Fysiogr. Sallsk. Hand!., newser., vol. 45, No. 11, 1934, 



pp. 40, 45, 46, 48, 52, 53, 54, 57. 

 Heteromelra (part) A. H. CLARK, Vid. Medd. Nat. Foren. K0benhavn, 1909, pp. 164, 165, 193; 



Crinoids of the Indian Ocean, 1912, p. 127. 

 Craspedometra (part) GISIJSN, Kungl. Fysiogr. Sallsk. Handl., new ser., vol. 45, No. 11, 1934, p. 22. 



Diagnosis. A genus of Himerometridae in which P D is much longer and stouter 

 than P u which in turn is much longer and stouter than P 2 ; the division series are 

 narrow, strongly rounded dorsally, and widely separated laterally; the IIIBr series on 

 the outer side of each IIBr series are 4(3+4), but on the inner side usually 2; the 

 brachials are exceedingly short, discoidal, with produced and overlapping distal 

 ends. The species are large and robust with 20-62 (but seldom less than 30) arms, 

 which are 100 to 200 (commonly 130-150) mm. in length. 



Geographical range. From the Philippine Islands and the Macclesfield Bank 

 south to the Admiralty Islands, the Moluccas, the Kei Islands, and the Great Barrier 

 reef, Queensland, and westward to the Maldive Islands and the Persian Gulf. 



Bathymetrical range. From the shoreline down to 57 (?66) meters; chiefly littoral 

 and sublittoral. 



Remarks. The species of the genus Himerometra are very easily distinguished 

 from all the other forms in the family Himerometridae by the fact that P D is the 

 longest and largest pinnule, the pinnules succeeding gradually decreasing in size to 

 P 3 . In addition to the characteristic pinnule structure, the strongly rounded, narrow, 

 and well-separated division series and exceedingly short discoidal brachials are features 

 that aid in the prompt generic determination of the included forms. 



The six species of the genus recognized herein are divisible into three groups of 

 two each. 



The first group, including H. bartschi and H. persica, is rather sharply separated 

 from the others. The slender proximal pinnules of these two species, which have 

 carinate basal segments, resemble in structure the corresponding pinnules in certain 

 species of Heterometra very closely much more closely than they do the pinnules of 

 the other species of Himerometra and it is interesting to note that although P D is 

 almost invariably longer than P P and P P is longer than P lf in a specimen of H. bartschi 

 from the Kei Islands (see page 211) P P is slightly longer and usually somewhat stouter 

 than PP. In these two species also the pinnules following the enlarged proximal 

 pinnules have the basal segments strongly carinate, a feature common in the species 

 of Heterometra but not found in the other species of Himerometra. Another peculiarity 

 of these two forms is that their outer cirrus segments bear more or less prominent 

 spines instead of being smooth or bearing obsolescent tubercles. While these two 

 species can only be regarded as belonging to the genus Himerometra, with the other 

 species of which they agree completely in the structure of their division series and 

 arms, they are to a certain extent intermediate between the species in the second and 

 third groups within the genus Himerometra and the species of Heterometra. 



The species in these last two groups are abruptly separated from all the other 

 forms in the family Himerometridae by the enormous stoutness of the proximal pin- 

 nules. Indeed, pinnules of the type characteristic of these species are found else- 

 where only in the genus Cenometra of the family Colobometridae in which P 2 is simi- 



