SUBKINGDOM ECHINODERMATA. 



CLASS ECHINIDA. 



ORDER PERISCHOECHINIDA. 



FAMILY PALAECHINID.E, 



MELONITES INDIANENSIS, 11. sp. 



Plate I, Fig. 1, apical view. 



Our specimen is injured, iu a few jilaces, thoua'b it is not easy 

 to trace the outlines of the plates in the anibulacral depres- 

 sions, and hence they are not distiuouished in the illustration. 

 The central basal part is destroyed and the oral plates are 

 o'one. 



The form is strikingly melon-like, notwithstanding the depres- 

 sions at the poles. The vertical height is two and fifteen- 

 hundreths inches, and the transverse diameter is two and sixty- 

 five-hundredths inches. The surface of the plates is covered 

 with tubercles that formed the bases of spines. And some of 

 the spines may be seen scattered over parts of the anibulacral 

 depressions. The spines are minute, elongate, tapering, cylin- 

 drical in section, swollen a little at the basal extremity, and 

 about one-tenth of an inch in length. 



The interambulacral areas are lance-elliptical in outline, ab- 

 ruptly elevated from the anibulacral depressions, sharply 

 rounded at the apical pole, more gently rounded toward the 

 middle, while the middle part is only slightly convex. There 

 are six ranges of plates at the middle part, a little higher only 

 five, a little higher only four, and then there are only three, 

 which grow smaller and terminate each interambulacral area by 

 abutting a genital plate. There are from twenty to thirty 

 tubercles on the larger plates. 



