548 TRAXS. ST. LOUIS ACAD. SCIENCE. 



Description of new Palceozoic Echinodermata. 



By G. Hambach. 



ECHINOIDEA. 



PAL.ECHINID.E McCoy. 



Genus Melonitks Norwood and Owen. 



Melonites crassus, n. s. 



(PI. C. Fil,^ 1.) 



Body large, globose, like that of Melonites multipora, com- 

 posed of very thick plates. Ambulacral areas running nearly 

 equal in width and concave over the w^hole surface of the body, 

 and almost two-thirds as wide as the interambulacrum, with a 

 very high ridge in the centre, elevating its surface above that of 

 the interambulacral field and dividing the same thus into two deep 

 concave furrows. Plates composing the same are very irregu- 

 lar, wider than high, and numbering ten in a transverse row, of 

 which the tw^o middle ones, forming the ridge, are the largest 

 and twice or more as wide as the others, each being laterally 

 perforated by two pores, thus forming five double rows of pores 

 to each side of the ridge. Surface granulated and covered with 

 little spines of about ^ of an inch in length. Interambulacral 

 areas lanceolate in outline, moderately convex, but more so than 

 in Melonites multipara^ and nearly half as wide as the ambula- 

 crum ; composed of very large plates, of which the two lateral 

 rows are pentagonal, all the others mostly hexagonal, irregular, 

 wider than high, and as large as two and a half of the ambula- 

 cral ones ; counting five in the greatest width of the field and 

 gradually tapering off" in number. Surface granulated and cov- 

 ered with little spines of yig^ of an inch in length ; of these gran- 

 ules 45 to 68 may be counted on each of the larger interambula- 

 cral plates, according to size, and as many in proportion on the 

 ambulacral ones. Oral opening and genital plates not visible in 

 the specimen. 



