HAMBACH NEW PALAEOZOIC ECHIDONERMATA. 55 1 



Genus Arch^ocidaris McCoj. 

 Archaeocidaris Newberryi, n. s. 



(PI. D, Fig. 1) 



All the specimens I have seen and possess are so much dis- 

 torted as to make it impossible to give an accurate description of 

 the general shape of the body, though I believe it to be like 

 other Cidaridce. 



Plates of the interambulacral space large hexagonal and pen- 

 tagonal where they join the ambulacrum ; central tubercle papil- 

 liform with a double annulation at the summit, of which the outer 

 one is the largest surrounding the crateriform tubercle in the cen- 

 tre ; margin of plates elevated and ornamented by a row of gra- 

 nulation. Ambulacral plates very small, elongated, nearly three 

 times as long as wide, and perforated by two pores. Spines 

 elongated, slightly compressed in the upper part, lower portion 

 round, a little contracted and bent above the crenulated annu- 

 lation of the articulation extremity ; surface very finely striated 

 and ornamented with small ascending spines. Their greatest 

 diameter is about one-third the length above the base. Length 

 of primary spines of a large specimen 35 inches,' tapering down 

 to almost \ an inch ; length of spines covering the margin granu- 

 lations, about \ of an inch. 



This species differs from Archceocidaris Shumardi Hall, in 

 the more robust form of its plates and spines, which are very 

 finely dotted in the two upper thirds of the spine in Shumardi^* 

 as well as in the double annulation of the central tubercle. 



Geological formation and locality — In the lower St. Louis lime- 

 stone, St. Louis, Missouri. Specimen in the collection of the 

 Washington University. Named in honor of Prof. L S. Newber- 

 ry, of Columbia College, New York. 



BLASTOIDEA. 



Genus Pentremites Say, n. s. 



Pentremites Sampsoni, n. s. 



(PI. D, Fig. 2, 2«.) 

 * See I. Hall's Geological Survey of Iowa, vol. i., pt. ii., pi. 26, fig. 3. 



