Vol. VI, No. 1.] On Clvpeaster duncanensis. 21 



[N.S.] 



From these dimensions the following ratios are ob- 



tained: 



(i) (fi) 



b:a 0*89 0*90 



c : b . . . . - . ? 0-65 



These ratios show that with the growth of the test, the re- 

 lative dimensions of the species in the different directions are 

 a little variable. 



The figures obtained for A , B and C, taken in considera- 

 tion with the above remarks, clearly point out the proba- 

 bility of A, B and C as belonging to the same species. It may 

 also be mentioned that the portion of the base that is preserved 

 in Dr. Noetling's type indicates a slight convexity in the 

 median interradial line with slight concavities on the two 



sides, a feature which is also found in C. complanaius \ 



From the foregoing considerations it appears to me that 

 there is probably no specific difference between C. complanatus, 

 Duncan and Sladen, and C. duncanensis, NoetL, and that the 

 latter is only a large sized representative of the typical Gaj 

 species with a base of about 74 mm., and that the specimen col- 

 lected by Mr. Vredenburg from the province of Kelat is inter- 

 mediate between these two. 



