342 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



land coast and the region northward to Singapore, the Philippines, and Formosa. 

 Still farther eastward, in southeastern New Guinea, Tonga, and Fiji, it is repre- 

 sented by the still smaller and slenderer papuensis. Many specimens from northern 

 Australia are intermediate between tessellata and discoidea, and specimens from 

 southeastern New Guinea are more or less intermediate between discoidea and 

 papuensis. 



The group of species including spectabilis, molleri, and pinniformis seems to be 

 distinct from the tessellata group ; but certain specimens of tessellata approach specta- 

 bilis rather closely, and some specimens might be assigned almost equally well either 

 to molleri or to discoidea. 



The relation between Amphimetra spectabilis and A. molleri is much the same as 

 that between tessellata and discoidea, and it may be that spectabilis is simply a large 

 local form of molleri. Probably pinniformis is simply a small local form of molleri 

 at any rate it appears to be very closely related to it. 



The color of the various forms is to a certain extent distinctive. Thus tessellata 

 is always very dark, varying (in alcohol) from dark brownish red to deep purple or 

 black, discoidea is lighter, ventrally yellow-brown to violet or purple and dorsally 

 grayish white or flesh color with the cirri becoming purple distally, though occasionally 

 unicolor and dark like tessellata, and papuensis is, like tessellata, uniform dark red- 

 brown. The two known specimens of spectabilis are both light and grayish white 

 with the ventral surface darker, and molleri is usually gray or light grayish brown, but 

 it may be reddish brown, yellowish brown, deep purple, or violet, or the dorsal skeleton 

 may be white or whitish and the ventral surface dark. A. ensifer varies from nearly 

 white to dark yellowish or purplish brown with the perisome and the ends of the cirri 

 darker, and laevipinna is light brown with purplish bands on the arms, or plain 

 grayish or brownish white. 



Though the color of the species of Amphimetra is more closely correlated with the 

 systematic interrelationships than is the case with most comatulids living in shallow 

 water, it is by no means to be relied upon as an indication of the systematic affinities 

 of any individual specimen. 



Although the exceedingly short brachials, resembling those of the species of 

 Himerometra and of many of the species of Heterometra, appear conclusively to 

 indicate that Amphimetra finds its proper place in the family Himerometridae, this 

 genus presents certain features suggesting an approach to the Colobometridae. 



In A. tessellata tessellata occasional specimens are found having more than 10 arms, 

 in which case the IIBr series are always 2 as in Cenometra, Cyllometra, and Epimetra 

 in fact in all the multibrachiate genera except Petasometra of the Colobometridae. 

 Also in A. tessellata tessellata the dorsal processes on the cirrus segments are occasion- 

 ally broadened laterally, forming a transverse ridge or paired spines in the fashion so 

 characteristic of the species of Colobometridae. The enlarged lower pinnules in the 

 species of Amphimetra are by no means so highly modified as they are in the other gen- 

 era of the family Himerometridae. They show an approach to the conditions in the 

 more generalized species of Decametra and Oligometra, this approach being especially 

 close in A. tessellata papuensis, in which the lower pinnules are unusually slender. 



