RE-CLASSIFICATION OF MULLERIA AND HOLOTHURIA. 167 



five-rayed appearance in the contracted condition. It is not 

 difficult to understand how these groups of papillae may be 

 converted first into eminences very richly provided with 

 spicules, and later into five calcareous masses. The presence 

 of anal teeth in Actinopyga and Argiodia does not necessarily 

 point to a close relationship between the two sub-genera, and 

 it is possible that in the group under discussion, as in some of 

 the Dendrochirotse, these structures have little or no phyletic 

 significance, and may have arisen independently in the two 

 sub-genera. 



Affinities of the five Sub genera. 



Taking thes'= four characters and applying them to the five 

 i=ub genera, we find that with regard to the ambulacral 

 appendages Actinopyga is the most primitive, since, with few 

 exceptions, the pedicels are arranged in three rows on the 

 trivium. In Bohadschia, which in other respects shows close 

 affinities with Actinopyga, the pedicels are scattered over the 

 trivium, with the notable exception of Bohadschia grdffei. 

 The species of the sub-genus Bohadschia are described by 

 many as having pedicels all over the body. If such be the 

 case, this would strengthen the claim of Bohadschia to be 

 considered the most primitive member of the genus. Thymio- 

 sicya, with its complete lack of true pedicels, may be regarded 

 as the most highly specialized. 



The evidence of the spicules points to Actinopyga and 

 Bohadschia being the most primitive sub -genera, and also 

 indicates their close relationship. The same conclusion is 

 forced upon one by a comparative study of the calcareous 

 ring. 



I have already pointed out how the pentagonal anus of 

 Bohadschia may be more primitive than the condition of 

 things seen in the other sub -genera, and that the anal teeth of 

 Actinopyga and Argiodia may be readily derived from the 

 condition of things found in Bohadschia. 



The weight of evidence goes to show that Bohadschia and 

 Actinopyga are more closely related to each other than to the 



