294 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



In one genus (Comatula) the synarthry between the elements of the IBr series is 

 replaced by a syzygy and the first 2 brachials are united by syzygy excepting only 

 in certain individuals of two species (pectinata and purpurea). 



The IIBr series, when present, are of two elements which are usually united by 

 a more or less perfect syzygy, and on the outer arms arising from a IIBr series there is 

 a syzygy between brachials 1 +2 as well as between brachials 3 + 4, which is usually 

 absent on the inner arms. The arm division, therefore, is of the same type as that 

 characteristic of Comatella and Neocomatella. 



In the exceptional individuals of Comatula pectinata which have more than 10 

 arms the additional arms arise in the usual way through loss of the original arm at 

 the articulation between the first 2 brachials and the appearance on the stump of an 

 axillary from which 2 similar arms arise. 



But in Comatula rotalaria the original arms are not lost. The very young have 

 10 arms only. As they grow, in place of the usual PI there appears on each arm an 

 arm bud which rapidly develops, forming a secondary (external) arm which reaches 

 full size at about the same time as the primary arm which bears it. This type of arm 

 reduplication is unique among the comatulids, but it should be considered in connec- 

 tion with the reduplication of the radials and postradial series in Promachocrinus. 



Excepting in a single genus (Comatula) the cirri are always well developed, there 

 being at least one complete row and usually more. In Comatula they may be in adult 

 individuals wholly absent (rotalaria, cratera, and micraster), confined to the inter- 

 radial angles of the centrodorsal where they occur singly or in pairs (purpurea and 

 tenuicirra), irregularly deficient (some individuals of solans and pectinata), or forming 

 a complete circlet (most examples of sola/is and pectinata). 



The cirri are always wholly devoid of dorsal processes, except for a more or less 

 developed opposing spine, composed of subequal segments which may be very short 

 (Comatulella) or moderately long, and strongly recurved. They are usually short and 

 stout, but exceptionally (Comatulides) rather long and slender. 



Increase in the number of arms over 10 and partial or complete absence of cirri 

 are confined to species or individuals occurring within the area bounded by Hong 

 Kong, the Philippines, tropical Australia, and Ceylon. It may be recalled that it is 

 only within this area that the species of Capillasterinae without cirri (Capillaster 

 macrobrachius) is found. 



History. The subfamily Comactiniinae was established in 1909 to include the 

 genera Comatula, Comactinia, and Cominia; the last name, being preoccupied, was 

 later changed to Comatulides. The genus Comatulella was subsequently created for 

 a species (brachiolata) at that time included in Comatula. 



The Comactiniinae include all of the species referred by Dr. P. H. Carpenter to 

 the Solaris group (herein included in the genera Comatula and Comatulella) ; one of the 

 two species (paucicirra = rotalaria) included in the Paucicirra group, the other, not 

 mentioned by name in the Challenger report but subsequently described as Actino- 

 metra notata, being a synonym of Comatella stelligera, a member of the subfamily 

 Capillasterinae; and two of the forms (echinoptera and meridionalis) definitely referred 

 to the Echinoptera group. Carpenter also referred to the Echinoptera group (Neo- 

 comatella) pulchella and (Nemaster) rubiginosa, both of which belong to the Capil- 



