REVISION OF THE ORINOID GENUS HIMEROMETRA. 



By Austin Hobart Clark, 



Assistant Curator, Division of Marine Invertebrates, United States National Museum. 



HISTORY OF THE GENUS. 



The fii'st known species of the genus Himerometra was described 

 by P, H. Carpenter in 1881 under the name of Actinometra robus- 

 tipinna. Looking backward at Carpenter's work from our present 

 vantage point which we have reached through the gradual accumu- 

 lation of facts extending over a period of more than 30 years, it 

 seems to us somewhat extraordinary that Carpenter should have 

 referred this form to the genus Actinometra instead of to the genus 

 Antedon as, using the systematic scheme of the day, he ought to 

 have done; but it was a very natural thing to do — in fact it is diffi- 

 cult to see how he could have done otherwise, for the single specimen 

 known to him is without a disk and without cirri, and is so badly 

 broken that only a single one of the enlarged proximal pinnules is 

 reasonably complete. He knew of no " tridistichate " Antedon in 

 which the size of the lower pinnules decreases from the "distichal 

 pinnule" outward, though this is the usual condition in the 'Hri- 

 distichate" species of Actinometra; therefore, as the disk and tips of 

 the lower pinnules, upon which he chiefly rehed in separating Antedon 

 from Actinometra, were absent, he very logically placed the species 

 in the latter genus. 



But the reference of robustipinna to Actinometra instead of to 

 Antedon, however natural it may have been, was most unfortunate, 

 for all subsequent students have accepted Carpenter's generic de- 

 termination, so that the species has remained entirely outside of the 

 literature on the group to which it belongs, and instead has assumed 

 a position in another group with which it has nothing whatever to do. 



In 1890 Hartlaub described as new three additional species of this 

 genus, redescribing them in greater detail and figuring them in 1891. 

 Two of these new species {Antedon martensi and Antedon Icraepelini) 

 he placed side by side in a new section of the "Savignyi group" of 

 Carpenter's classification characterized by the presence of palmar 



Proceedings U. S. National Museum, Vol. 46— No, 2026. 



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