78 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



sometimes repeated, reduced in size, on the inner ventral edge. (Vol. 1, pt. 2, 

 pp. 311, 319, pi. 17.) 



The anal tube usually occupies a position at or near the center of the disk, the 

 mouth being marginal and situated in a peripheral groove, interrupted posteriorly, 

 into which run the ambulacral grooves from the arms (vol. 1, pt. 2, pi. 24); but rarely 

 the mouth is central with 5 groove trunks radiating from it, and the anal tube is 

 marginal or submarginal (vol. 1, pt. 2, figs. 686, 687, 697, 698, p. 341). 



Sacculi are absent, excepting in Comatonia and ComatiUa. 



In very many species more or fewer of the arms are ungrooved (vol. 1, pt. 2, 

 pp. 91 , bottom, to 95), and these may be much shorter than the other arms. (Vol. 1 , 

 pt. 2, fig. 163, p. 86.) 



The arms are 10 or more in number, but usually more than 10. 



In many Indo-Pacific species, and in a greater or lesser proportion of the indi- 

 viduals in others, the centrodorsal is reduced to a pentagonal or stellate plate and is 

 quite without cirri. (Vol. 1, pt. 1, figs. 165-170, p. 229.) 



Geographical range. — From Japan and PoljTiesia to New Zealand and Tasmania, 

 and westward to the entire eastern coast of Africa; from Brittany to the Canary 

 Islands, and from North Carolina to Rio do Janeu-o, Brazil. 



Bathymetrical range. — From the shore line down to 1,710 meters; but the great 

 majority of the species are littoral and sublittoral. 



History. — The first student of the Crmoidea definitely to set off from the re- 

 mainder of the comatulids any member of this group was Louis Agassiz who in 1836 

 established the genus Comaster which was based upon the Comatula multiradiata of 

 Lamarck. The only character he gave for his new genus, however, was the posses- 

 sion of more than 10 arms. 



In 1840 Johannes MuUer examined in the Vienna Museum a very large dried 

 specimen of Comatula Solaris. This he made the type of a new genus which he called 

 Adinometra in 1841, describing it under the name of Actinometra Imperialis. He 

 remarked that the animal in question, Comatula Solaris Mus. Vienn., one of the 

 colossal forms of living crmoids, has no trace of grooves running to the center of the 

 disk. The middle of the ventral surface of the disk is occupied by a tube. The arms 

 are provided with grooves, the grooves from the 1 arms debouching at regular inter- 

 vals into a circular groove running about the periphery of the disk. He was unable 

 to find the mouth. The other characters, he said, were the same as in the other 

 comatulids. In 1841 he also discussed Agassiz' geniis Comaster, but he assumed that 

 it was based upon the Comatula multriadiata described and figured by Goldfuss in 

 1832 instead of on the Comatula multiradiata of Lamarck. 



In 1843 Muller wrote that he had found the same disk structure in two other 

 comatulids in the museum at Lund. These were the two described by Retzius in 

 1805 as Asterias multiradiata and Asterias pedinata, and were the types of the Linnean 

 species of the same names. 



In his monograph published in 1849 Muller used the generic name Comatula for 

 all the comatuhds. The species in which five radiating grooves reach the disk he 

 assigned to the subgenus Aledo, which he placed in parentheses after Comatula, while 

 those species in which fewer than five grooves reach the disk he assigned to the sub- 



