A MONOGRAPH OF THE EXISTING CRINOIDS 75 



Oligophreaten A. H. Clark, Die Crinoiden der Antarktis, 1915, p. 167 (of the 7 South Australian 

 crinoids, 5 belong to this suborder). 



Diagnosis. — A suborder of Comatulida in which the cavity in the centrodorsal 

 containing the chambered organ and overlying structures is very small and shallow ; 

 the rosette is sunk below the dorsal surface of the radial pentagon, and both the 

 radial and interradial extensions form "spouthke" processes; the central portion 

 of the radial pentagon is more or less completely filled with an irregular calcareous 

 deposit which forms a central plug; the plane of the muscular fossae on the radial 

 articular faces makes a considerable angle with the dorsoventral axis, or the muscular 

 fossae are very greatly reduced; the joint face elements distal to the transverse 

 ridge are not at all, or are only slightly, excavated interiorly; the brachials from 

 about the fourteenth onward are usually short, generally much broader than long; 

 the second brachial syzygy is almost invariably beyond the ninth brachial; the 

 brachial syzygies are usually more or less widely and irregularly spaced; the pin- 

 nules, always the proximal and in some groups all, are wholly or in part prismatic 

 with a dorsal carination which may be confiiied to the earlier segments; segments 

 of the distal pinnules beyond the third not especially slender or elongated, and the 

 first 2 not appreciably broadened; never more than 5 radials; arms 10 or more in 

 number, very commonly more than 10. 



Geographical range. — Western Aleutian, Hawaiian and Galapagos Islands to 

 New Zealand and Tasmania and westward to east Africa and the Crozct Islands; 

 in the Atlantic from Tristan da Cunha and southern Brazil to Brittany and North 

 Carolina. 



This suborder is not represented in the Arctic or Antai'ctic regions, on the western 

 coast of North or South America, or in the Norwegian, Mediterranean, Bering, 

 Okhotsk, or Japanese Seas, except that it just enters the southeastern portion of 

 the last through the Korean Straits. 



Bathymetrical range.— From between tide marks down to 2,926 meters. 



Thermal range. — From the high temperatures of the tropical httoral down to 

 1.22° C. 



History. — The first attempt to divide the living comatulids into two large 

 groups was made by the present author in 1908 in the following words: 



The comatulids are divided into two great groups, one with triangular 

 pinnules and small eggs, the Thalassometroida, the other with round pinnules 

 and large eggs, the Antedonoida. 



The groups were not further defined at that time, nor were the included families 

 or genera mentioned. 



In 1909 these same two groups were distinguished as the Comatulida Oligo- 

 phreata and the Comatulida Macrophreata, and diagnoses were given. The families 

 included in the Comatulida Oligophreata were the Comasteridae, Zygometridae, 

 Himerometridae, Colobometridae, Thalassometridae, and Tropiometridae. At 

 that tune the family Zygometridae included the Eudiocrinidae, the Himerome- 

 tridae included the Mariametridae, the Thalassometridae included the Charito- 

 metridae, and the Tropiometridae mcluded the Calometridae. 



