140 



ECHINODERMATA. 



No. 429. [781, Cast]. Palaeechinus (Melonites) multipora, 



[Nor. and Owen. 



Group, on slab. This gigantic Echinoid — some specimens measuring five 

 and a half inches in vertical diameter and four transversely — has an ovoid 

 form, central mouth and anus, ten areas; the ambulacral plates hexagonal and 

 rhomboidal; interarabulacral plates mostly hexagonal , and in several rows. 

 The ranges of plates number 65. and each plate is perforated by two holes. 

 This genus is limited to the Upper Silurian and Carboniferous. Only one 

 other genus (Archaeocidaris) is known from the PalaBOzoic. From the St. 

 Louis limestone (sub-carboniferous), St. Louis, Mo. Size, 13 x 11. 



No. 430. Pygaster semisulcatus, Phil. 



Pea Grit (Lower Oolite), Chrichley Hill. England. 



No. 431. [789, Cast]. Rhabdocidaris copeoides, Desor. 

 (Cidaris copeoides, Agass.) 



Three specimens op spines. 

 This Urchin belongs to the Cidaridm 

 having narrow umbulacra. The 

 spines vary very much in size and 

 form on different parts of the test, 

 and at different stages of develop- 

 ment. From the Oxfordian (Middle 

 Oolite), Latrecy, France. 



No. 432. Scutella disca, Mather. 



This Amei'ican Clypeastroid is from the Tertiary of 

 Georgia. 



No. 433. Toxaster Texana, 

 Cretaceous, Lampasas Co., Texas. 



