52 . FOSSIL ECHINI OF THE WEST INDIES. 



Genus MELLITA Agassiz, 1841. 



Type species. — Scutella quinquefora Lamarck, 1816, Anim. sans Vert., 

 vol. 3, p. 9 = Echinodiscus quinquiesperforatus Leske, 1778, Add. ad 

 Klein, p. 133. 



Mellita species. 



(Text-figure 6.) 



The following is a description of this specimen : 



Test elliptical, a little longer than wide. Very small, low, thin, with 

 rounded edges. The ambulacral petals are rounded and rather short. A 

 small oval lunule is in interambulacrum 5, nearer to the posterior border 

 of the test than it is to the apical disk. There are slight emarginations in 

 ambulacra I and V, which appear to be the beginnings of lunules formed 

 by inclusion. The apical disk is central in position, but there are no genital 

 pores visible, although the specimen is very well preserved. It would seem 

 that the absence of the genital pores indicates the youth of the specimen. 



This specimen measures 7 mm. in length, 6 mm. in width, and 

 about 1 mm. in height. 



Comparing this evidently young individual with 

 material in the Museum of Comparative Zoology, 

 it is almost identical in structure with very young 

 specimens of Mellita sexiesperforata (Leske) of about 

 the same size. 



It seems at first sight unreasonable to assume that 

 the genus Mellita should be represented in the fossil 

 state in the West Indies only by a specimen of such 

 rarity as a very young individual. The only other F l %f~^"ou" T" 

 reasonable view would be to assume that it is an 

 adult, or at least relatively much older individual of a very small 

 species. It would then be most primitive in structure, would not fit 

 into the genus Mellita or any other genus at present known, and the 

 absence of genital pores, which is only a youthful character in Echini, 

 would not be accounted for other than by assuming rather extreme 

 youth. 



Miocene, Mayo Village Quarry (locality 11), Trinidad, F. W. 

 Penny collector, U. S. Geol. Sur. station 8583, U. S. Nat. Mus. No. 

 228244. 



Order EXOCYCLOIDA Jackson, 1912. 

 Suborder SPATANGINA Jackson, 1012. 



Of the Spatangina, there are many species occurring fossil in the 

 West Indies, and including those which have been published but of 

 which I have not seen material, there are more species than of all other 

 Echini put together. Notwithstanding their relative abundance, the 

 spatangoids are usually harder to study in that the material has 

 much thinner tests and is therefore much more fragile and usually is 

 not as well preserved. 



