no. 5 



TERTIARY ECHINOIDS FROM FLORIDA — KIER 



23 



Color. — Yellow-brown except for five brown specimens. 



Comparison with other species. — This species is most similar to 

 Clypeaster subdepressus. It differs in having a thicker margin, a 

 less elongate and less inflated test, and a flatter area between the ends 

 of the petals and the margin. Petal III in C. prostratus is more open 

 and shorter relative to the other petals, and the paired petals are more 

 constricted distally. The basicoronal interambulacral plates do not 



Figs. 15, 16. — Clypeaster prostratus (Ravenel) : 15, Adoral view of U.S.N.M. 

 648176, from the Recent, Gulf of Mexico, lat. 29° 10' N., long. 85° 31' W., Alba- 

 tross station 2375, X 1 ; 16, exterior and interior views of basicoronal plates of 

 U.S.N.M. 648173 from same locality as above, X 3. 



