90 BULLETIN 8 2, UNITED STATES NATIONAL MUSEUM 



It is possible that marginata, which is based upon unmature individuals, will prove to 

 be merely an immature form of anisa. 



History. — In spite of the striking uniformity in details characteristic of the 

 included species, the history of this genus is smgularly involved. The first species 

 known was described by Dr. Clemens Hartlaub in the genus Antedon. Hartlaub 

 said that this form {Antedon japonica) is very similar in its habitus to Antedon serri- 

 pinna and that it is very likely that a further knowledge of the two will lead to their 

 eventually being united. 



In my first revision of the old genus Antedon in 1907 I retained japonica in the 

 genus Antedon, but upon the establishment of the new genus Oligometra in 1908 

 japonica was transferred to it, and here it has remained until the present time. In 

 1912 I described a second species {marginata) in the genus Oligometra, saying that it 

 was most closely related to 0. adeonae. In 1915 Dr. Hubert Lyman Clark described 

 a third species {anisa) in the genus Oligometra, which he said was no doubt related 

 to 0. carpenteri. In 1918 I placed my Oligometra marginata and Dr. H. L. Clark's 

 0. anisa in the synonymy of Oligomeirides adeonae, leaving japonica in the genus 

 Oligometra. 



In 1920 I described a new species from the Philippine Islands under the name of 

 Oligometrides bellona. 



In 1929 I established the genus Iconometra for a new species {speciosa) from the 

 coast of Annam. I said that this new genus is most closely allied to Oligometrides 

 from which, however, it appears to be quite distinct. In addition to the type species, 

 speciosa, I included in it Doctor Clark's anisa and my own bellona. 



Up to the present time japonica has remained in the genus Oligometra, being 

 regarded, largely on the basis of Hartlaub's statement, as a smooth pinnuled form of 

 0. serripinna, and marginnta has been left in the synonymy of Oligometrides adeonae. 



KEY TO THE SPECIES IN THE GENUS ICONOMETRA 



a>. About 20 arms; Pi, Pz, and P3 of about the same length; P4 scarcely more than half as long as the 

 pinnules preceding; cirri with 20-23 segments, about 13 mm. long; arms 75 mm. long (off 



southern Annam; 146 meters) speciosa (p. 91) 



o^. Arms 10 or 1 1 in number. 



b'. More than 20 cirrus segments; Pj and P3 similar and of nearly or quite the same length; Pi 

 similar, but shorter, 

 c'. Transverse ridge on the cirrus segments proximal; 11 arms about 100 mm. long (Philippine 



Islands; 0-16 t?73] meters) bellona (p. 93) 



(?. Transverse ridge on the cirrus segments at first subterminal, later becoming median; 10 arms 



40-75 mm. long (Sagami Bay, Japan; 0-46 meters) japonica (p. 94) 



6'. Fewer than 20 cirrus segments; Pj shorter than P2. 



c'. Pj markedly longer, as well as stouter, than Pi; proximal pinnules with 10-16 segments; 

 cirri XVI-XXIII, 15-19, 10-12 mm. long; 10 arms 45-65 mm. long (Torres Strait to 



Amboina; 0-100 [7130] meters) anisa (p. 97) 



c'. Pi slightly longer than Pj; proximal pinnules with 8 or 9 segments. 



dK Pj slightly stouter than Pi; cirri XV, 15-16, 7 mm. long; 10 arms 30 mm. long (Solor 



Strait; 113 meters) marginata (p. 103) 



d^. P2 exactly resembling Pi; cirri IX, 10-11, 2.5 mm. long (Andaman Islands). 



intermedia (p 103) 



