A MONOGRAPH OF THE EXISTING CRINOIDS 257 



them. The centrodorsal is lai^e with the cirri arranged more or less regularly in 15, 

 or sometimes 20, closely crowded columns. The cirri are very long with very numer- 

 ous segments of which the outer bear dorsal spines. As in the Tropiometridae and 

 Calometridae, the articular faces of the radials are verj' distinctive; the intcrarticular 

 ligament fossae are low triangles and the muscular fossae are reduced to narrow bands 

 along their distal edge (see Part 2, pp. 42-44). 



In general the species of the family Asterometridae resemble those of the family 

 Ptilometridae, but the centrodorsal is small and more or less conical with the cirri 

 arranged in 10 definite and usually well-separated colunms; the cirri are larger and 

 stouter and less numerous; and the division series and arm bases are narrower and 

 more compressed with the component ossicles deeper and more broadly flattened 

 laterally. The articular faces of the radials are essentially similar to those of the 

 family Thalassometridae (see Part 2, pp. 44-45, Asterometra macropoda). 



The numerous species of the family Thalassometridae vary from small to very 

 large. The pinnules are prismatic and stiff, the distal sometimes becoming more or 

 less flexible, with well developed side- and covering-plates. Pi is longer and stouter, 

 often much longer and much stouter, than the pinnules immediately following, which 

 are always short. The centrodorsal varies from small and conical to large and thick 

 discoidal, with the cirri usuaUy in 10 or 15 regular columns, sometimes in more or less 

 irregular rows. The cirri are usually long and rather slender with a wcU-developed 

 transition segment beyond which the segments almost invariably bear prominent dorsal 

 spines. The articular faces of the radials are essentially similar to those of the family 

 Asterometridae; they differ from those of the family Charitometridae in having the 

 very long muscular fossae parallel, making an obtuse angle with the intcrarticular 

 ligament fossae (see Part 2, pp. 45-48). 



The species of the family Charitometridae resemble in the main those of the 

 Thalassometridae, but Pi and Pj, rarely only Pi, are slender and are composed of 

 numerous short segments, and the cirri are short, stout, strongly recurved, and com- 

 posed of few segments none of which bear dorsal spines. The articular faces of the 

 radials resemble in general those of the Thalassometridae, but the muscular fossae 

 lie approximately in the same plane as the intcrarticular ligament fossae, and therefore 

 distally (see Part 2, pp. 48-49). 



The superfamily Tropiometrida, like the superfamily Mariametrida, is most 

 strongly represented in the area from southern Japan to Australia. The family 

 Asterometridae ranges from southern Japan and the Bonin Islands southward to the 

 Kei and Lesser Sunda Islands and the western coast of the Malay Peninsula in from 

 5 to 256 meters, and the Calometridae ranges from southern Japan to tropical Western 

 AustraUa and westward to the Andaman Islands in from 5 to 600 meters. These 

 two families, therefore, have approximately the same range as the families Zygo- 

 metridae and Eudiocriuidae in the superfamily Mariametrida, though they descend 

 to considerably greater depths. The family Ptilometridae is confined to southern 

 Australia, the species living from the shore line to a depth of 113 meters. In the 

 superfamily Mariametrida a single species {Austromctra thetidis) of Colobonictridae 

 occurs in the northeastern portion of its territory. The family Tropiometridae ranges 

 from southern Japan to northern Australia and westward to east and South Africa, 

 St. Helena, and the western Atlantic from southern Brazil to St. Lucia, Trinidad, and 



