2. On a probable identity between Clypeaster com/tiff 



natns, Duncan and Sladen, and Clypeaster 



duncanensis, Noetling'- 



By Hem Chandra Das- Gupta. 



1886. Clypeaster complanatus, Duncan and Sladen, in Pal. 



Ind., Ser. xiv., Vol. I., 3 fasc, v, p. 325, pi. L. 

 1901 . Clypeaster duncanensis, Noetl. , in Pal. Ind. , New Ser. , 



Vol. I., pt. 3, p. 105, pi. I, fig. 13. 



While arranging the duplicates of Clypeaster described 

 from the Indian Tertiaries I had an opportunity of studying 

 Clypeaster duncanensis, Noetl., from the miocene beds of 

 Burma occurring at an ' unknown horizon near Prome.' Dr. 

 Noetling believed this species to be quite different from any of 

 the species previously described from Western India but com- 

 pared it, among others, with Clypeaster complanatus, Dune, and 

 Slad. Dr. Noetling, however, thought that these two species 

 could be distinguished by (1) the large size, (2) the small base 

 and (3) the nature of the poriferous zones in the type from 

 Burma. In plate I, fig. 13, of Dr. Noetling 's monograph there 

 is a restoration of the species, and on a careful examination of 

 the restored figure two features stand out prominently. In the 

 text it is mentioned that the length is greater than the breadth, 

 but the length of the restored specimen is 100 mm. while that 

 of the greatest breadth is 107 mm. Dr. Noetling's specimen 

 which is in a fragmentary state shows parts only of the ambul- 

 acra! petals III and IV and a very small portion of Va. A 

 careful measurement of the angles between the adjacent me- 

 dian-lines of the ambulacral petals as restored by Dr. Noetling 

 gives the following results : 



Between the median-line of I and that of II . . 70° (a) 



99 5? 



5, 53 



79 9) 



II „ III . . 76° (/?) 



III „ IV .. 76° ( 7 ) 



IV ,, V .. 64° (S) 



V „ I .. 74° (c) 



In the measurements given above the differences between 

 (a) and (8) are very striking, showing clearly that the relative 

 lines of the ambulacral petals must be quite different from what 



find 



Noetlin 



large size attained 



by his species; but in the collection of Mr. Vredenburg from 



