4 PLEIOCENE FOSSILS. 



others. The ambulacral furrows on the lower surface are less branched than in M. hexa- 

 phora. These characters likewise separate this fossil from M. similis, Agass. This is the 

 lowest formation in which the genus Mellita has as yet been found. 



The dimensions of an imperfect specimen, kindly lent us by Dr. Edmund Ravenel, of the 

 Grove Plantation, Cooper River, are, Lon. 5| in., Lat. 5 J, Alt. J. The original of our 

 drawing measures, Lon. 2 J, Lat. 2, Alt. \. 



Plate L, Fig. 4. Upper surface. 

 " 45. Lower surface. 

 " 4a. Profile. 



Locality. — Cooper River, Goose Creek and Wadmalaw River. 



Museum, College of Charleston. 



PSAMMECHINUS.— Agassiz. 

 PSAMMECHINUS EXOLETTJS.— McCsady.— {New Specks.-) 



Plate II., Fig. 6. 



Psammechinus tuberculis ambulacralibus parvis, numerosis, frequentibusque. 



Description. This small relic is hardly more than an indication of the existence of a 

 new species. Fig. 6 is an enlarged view of the fragment, which is the upper end of one of 

 the ambulacra and a somewhat injured piece of the inter-ambulacrum of its left side. The 

 arrangement of the pores in broken rows of three pairs each betrays one of those generic 

 types allied to the true Echinus, and the two regular rows of large tubercles in the ambu- 

 lacrum and the single row of still larger knops on the inter-ambulacrum, with the clear 

 space between this row and its left edge, seem to assign it to the sub-genus Psammechinus 

 of Agassiz, which is quite removed from the ordinary Echinus by the prominent scales on 

 its buccal membrane. A species of this genus is now living on our coast, still undescribed, 

 from which this fossil appears to differ in having the tubercles of its ambulacral series 

 relatively smaller, more numerous and crowded. 



Plate II. , Fig. 6, is a view of the fragment enlarged to about twice the natural size, to show the 

 arrangement of the pores. 



Locality. Smith's, Goose Creek, S. C. (J. McC.) 



