416 



PROF. P. M. DUNCAN ON ECHTNOIDEA 



remarked that he had compared the specimens identified with Cly- 

 peaster folium with Monostychia austrcdis, Lauhe, and that he fonnd 

 them one and the same. In 1877 I accepted Mr. E. Etheridge's 

 correction with a necessary explanation (Quart. Journ. Geol. Soc. 

 vol. xxxiii. p. 48). But there is at least one excellent specimen of a 

 Clypeaster in the National Collection (Blanford Coll., Geelong, 

 Victoria E. 1,108, marked X), and it has the specific characters of 

 Clypeaster folium, Agass. The specimen was compared with a small 

 Clypeaster folium from the Miocene of Corsica, in the British 

 Museum, and with a full-grown type from Malta, also in the 

 National Collection ; careful measurements were taken, and with the 

 following results : — 



The relational measurements of a small Clypeaster folium from 

 Corsica (length 47 millim. ; 47=100): length 100, width 9o-7, 

 height 17. The measurements of the large type from Malta, the 

 length being 93 millim : length 100, width 86, height 18*4. 

 The measurements of the middle-sized specimen from Geelong 

 (length 66 millim) : length 100, width 84-8, height 17*4. The 

 comparison of these measurements with those taken by M'Coy of 

 Clypeaster gippslandicus shows that the height of that form is 

 much greater than that of Clypeaster folium, being 27 in relation 

 to 100. In the form which I consider to be a mere variety of 

 Clypeaster folium, Agass., the petaliferous part of the ambulacra is 

 very slightly raised and the flatness of the test is very marked. 

 But there are the same characters, regarding shape and relative size, 

 in the petals of the three specimens measured. In a typical 

 Clypeaster folium the anterior petal is the longest, and its breadth 

 is the same as that of one of the antero-lateral petals, which is, 

 however, shorter ; the postero-lateral petals are the shortest and 

 widest. The measurements in the Australian type are : — anterior 

 ambulacral petal 18 millim. long and 12 millim wide ; antero- 

 lateral petals 16 millim. long and 12 millim. wide ; postero- 

 lateral petals 11 millim. long and 13*5 millim. wide. The anterior 

 petal is widely open, and the postero-lateral are less so, but are 

 large distally, and the antero-lateral petals are nipped in near 

 the end where the pores of the opposite zones approach to a con- 

 siderable extent. This narrowing of the distal ends is very striking 

 and persists in all the specimens. 



The shape of the test of the Geelong form is rather longer than is 

 usual in European specimens, and there is perhaps a little more 

 rounding of the thin posterior margin of the test. The shape 

 differs materially from that of Clypeaster gippslandicus, M'Coy, 

 and the ornamentation of the costse of the poriferous zones and of 

 the test between the tubercles is also different in the two forms. 



If the Geelong Clypeaster had been found in Malta, it would have 

 been put down at once as a variety of Clypeaster folium, and I 

 therefore give it that name. 



9. Clypeaster gippslandicus, M'Coy, 1879 *. 

 Echinantlius Ustudinarius, Gray. 



Prof. M'Coy considers that Echinantlius testudinarius, Gray, which 

 * Prodr. Pal. Vict. dec. vi. 1879, p. 33. 



