344 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



Carpenter said that the special character that distinguishes the Milberti group is 

 the large size of one or more of the second, third, and fourth pairs of pinnules, and 

 remarked that this feature is well shown in anceps (= Heterometra quinduplicava, 

 10-armed individuals), milberti ( tessellata, or more likely, molleri), variipinna 

 (=Heterometra crenulata, 10-armed individuals), and also in some species described by 

 Bell in the Alert report, while it reappears in a more marked degree in some of the 

 multibrachiate species. He noted that in some cases, as in milberti (referring chiefly 

 to molleri), the second, third, and fourth pairs are all of greater size than the pinnules 

 above and below them, sometimes the second and sometimes the third pairs being 

 the largest. He remarked that in anceps (= 10-armed individuals of Heterometra 

 quinduplicava) and in variipinna (= 10-armed individuals of Heterometra crenulata) 

 the pinnules of the fifth or sixth brachials (P b and P 3 ), or both, are considerably longer 

 and stouter than their fellows, and in carpenteri (=0ligometra carpenteri) and in pumila 

 (=Compsometra loveni) the large pinnule is on the fourth brachial (P2). But in 

 carinata (= Tropiometra carinata) and in parvicirra (=Dorometra parvicirra) the 

 third and following pairs of pinnules are much more equal in size. 



At the end of the Milberti group Carpenter placed two "abnormal" species, 

 informis (= Decametra informis) and loveni (= Colobometra perspinosa), in which P a 

 is absent, though in other respects, he said, they conform pretty well to the general 

 type. 



In my first revision of the genus Antedon published in 1907 the species placed by 

 Carpenter in the Milberti group were distributed hi the following genera Himero- 

 metra (milberti, tessellata, anceps, and variipinna) ; Antedon (serripinna, carpenteri, 

 pumila, and parvicirra) ; Cyllometra (perspinosa, informis, and loveni [renamed Cyllo- 

 metra belli]) ; and Tropiometra (carinata) ; pinniformis and laevissima were not men- 

 tioned. 



Toward the end of 1908 I described Himerometra molleri, H. schlegelii, H. producta, 

 and H. ensifer from specimens in the collection of the Zoological Museum at Copen- 

 hagen, and about two weeks later I described H. discoidea from specimens in the 

 United States National Museum. 



In the revision of the family Himerometridae published in 1909 I established the 

 new genus Amphimetra with Comatula (Alecto) milberti J. Miiller, 1846, as the geno- 

 type, including in it anceps, ensiformis (sic), laevissima, milberti, molleri, producta, 

 schlegelii, tessellata, and variipinna. 



In the key to the genera of Himerometridae Amphimetra was paired with Himero- 

 metra, these two genera being differentiated from all the related genera by having 

 the middle and distal brachials extremely short and oblong, and the elements of the 

 IBr series and lower brachials strongly convex dorsoventrally, appearing swollen. 

 From Himercmetra it was separated by having the IBr series and first two brachials 

 in apposition for their entire length, strongly developed synarthrial tubercles, P! 

 smaller and slenderer than P 2 , and 10-20 arms, whereas in Himerometra the division 

 series are rounded dorsally and widely separated laterally, synarthrial tubercles are 

 not developed, P! resembles P D and P P and is larger than P 2 , and there are more than 

 25 arms. 



Later in 1909 I described Amphimetra mortenseni (June 19) and A. parilis (August 

 23). 



