24 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



detail. The brachial articulations are minutely described and are divided into two 

 types, muscular, with two subdivisions, straight and oblique, and nonmuscular, also 

 with two subdivisions, synarthri.es and syzygies. The ossicles of the division series, 

 no matter how many of them there may be, are shown to be repetitions of the first 

 two brachials at the base of the free undivided arms interpolated between the base of 

 the arms and the radials, excepting in a very few anomalous types This pair of 

 brachials is designated as the Z pair and is assumed to consist of the two components 

 Zi and Z 2 . Division series composed of simple repetitions of the Z pair interpolated 

 between the original Z pair and the radials are called interpolated division series, while 

 division series formed by a splitting of the arm at a certain ossicle which thereby 

 becomes an axillary are called extraneous division series. The conclusions reached 

 in this paper have for the most part been forecast in preceding papers. 



The anomalous arm structure of Comaster mariae, C. fimbriata, C. coppingeri, C. 

 borneensis, C. multiradiata, C. iowensis, C. sentosa, C. lineata, and C. discoidea is 

 explained by assuming that in these the Z pair is represented by the two segments 

 immediately following the costal (IBr) axillary and that all the division series beyond 

 the costals (IBr) are extraneous. 



On the basis of the type of arm division the comasterids are distributed among 

 three genera, as follows: 



Comatula (genotype C. Solaris Lamarck, 1816) including 



Comatula distincta. Comatula paucicirra. 



Comatula multibrachiata. Comatula pectinata. 



Comatula notata. Comatula Solaris. 



Pfianogenia (genotype P. typica Love"n, 1866), including 



Phanogenia alata. Phanogenia nobilis. 



Phanogenia alternans. Phanogenia novae-guineae. 



Phanogenia belli. Phanogenia orientalis. 



Phanogenia bennetti. Phanogenia parvicirra. 



Phanogenia briareus. Phanogenia, peronii. 



Phanogenia carpenteri. Phanogenia quadrata. 



Phanogenia divaricata. Phanogenia regalis. 



Phanogenia duplex. Phanogenia robustipinna. 



Phanogenia echinoptera. Phanogenia rotalaria. 



Phanogenia elongata. Phanogenia rubiginosa. 



Phanogenia gracilis. Phanogenia schlegelii. 



Phanogenia grandicalyx. Phanogenia serrata. 



Phanogenia japonica. Phanogenia solaster. 



Phanogenia meridionalis. Phanogenia stelligera. 



Phanogenia littoralis. Phanogenia trichoptera. 



Phanogenia macrobrachius. Phanogenia typica. 



Phanogenia maculata. Phanogenia valida. 



Phanogenia magnifica. Phanogenia variabilis. 



