166 SPOLIA ZEYLANICA. 



CALCAREOtrs Ring. 



The primitive aspidochirote calcareous ring was composed 

 of ten simple pieces (five radials and five inter-radials) without 

 anterior or posterior prolongations (PI. XXVI., fig. 1). The 

 radial longitudinal muscles were attached to the radial pieces, 

 and in consequence these were notched anteriorly for the 

 insertion of the muscles, and because of this the radial pieces 

 were larger and stronger than the inter-radials (PI. XXVI., 

 fig. 2). The tentacular ampullae arose near the anterior end of 

 the calcareous ring, and in consequence the anterior end of the 

 ring became scooped out at twenty places (ampuUary notches) 

 corresponding to the twenty tentacles (PI. XXVI., fig. 3). 

 Such a type is seen in the sub-genera Actinopyga and Bohadschia 

 (PI. XXVI., figs. 4 and 5). In Bohadschia vitiensis the inter- 

 radials do not project so far forward as the radials. This 

 difference gradually becomes emphasized, and at the same time 

 the ampullary notches become less and less marked, until in the 

 sub-genera Argiodia, Halodeima, and Thymiosicya the ampul- 

 lary notches are rarely clearly marked, and there is a marked 

 difference between the radials and inter-radials in respect of 

 the amount of anterior prolongation. Coupled with this we 

 find that the anterior projections of the radials and inter- 

 radials are clearly separated by a deep indentation (PI. XXVI., 

 figs. 6, 7, and 8). 



Anal Teeth. 



The presence of anal teeth is not a primitive character, 

 although the anus of the primitive Holothurian was probably 

 pentagonal.* I am incHned to think that the appearance of 

 the anus in Bohadschia is more primitive than the conditions 

 in Halodeima and Thymiosicya. In the latter sub -genera the 

 anus is generally rounded, and the papillae are not grouped 

 around it in any definite manner. In Bohadschia the anus is 

 surrounded by five groups of papillae, which give the anus a 



* That is to say, in the contracted condition. In Bohadschia vitiensis 

 the pulsating anus is alternately rounded and pentagonal during the 

 conditions of diastole and systole, respectively. 



