PLATE 73. 



Lepidesthes extremis sp. nov. p agp 430 



Figs. 1, 2. Putnam Hill Limestone, Carboniferous (Coal Measures), New Lexington, Perry County, Ohio, collected by 

 Eber Hyde, who loaned the specimen, which is no. 525 of his collection. Paratype. Siliceous external molds. 



Fig. 1. Interambulacral plates, rounded in outline with secondary tubercles occurring as pits in the matrix. X 5 3 

 Fig. 2. Spines, slender and tapering. X 5.3. 



Pholidocidaris irregularis (Meek and Worthen). p age 434. 



Fig. 3. Same specimen as photograph, Plate 75, fig. 1. X 1.8. Dorsal view ; a fine delicately built test; apparently with 

 six columns of plates in an ambulacra! area, as indicated by three columns of plates in the right half of area D The 

 ambulacral plates are all small. There are six columns of plates in each of the two interambulacral areas preserved 

 columns 5 or 6 drops out early passing dorsally. Of the interambulacra, the adambulacral plates are much ih,' 

 largest, each with a large eccentric perforate primary tubercle and secondary tubercles. The plates of the middle 

 columns of the interambulacra have secondary tubercles only; all interambulacral plates are thin, scaly rounded 

 in outline and imbricating strongly dorsally and from the center laterally and over the ambulacrals. A genital 

 plate in area A has ten genital pores, and next to it a small plate, probably an ocular, has two pores (p 437) 

 Fig. 4. Same specimen as photograph, Plate 75, fig. 2. X 1.8. A very similar specimen to fig. 3. In interambulacral 

 area A, there are six columns, while in C there are only five columns of interambulacral plates, and in G there are 

 apparently only five, but in area I there are again six columns of plates. Two genital plates have numerous pores 

 each. Ambulacral plates are all small (p. 436). 



Fig. 5. The same specimen, a small primary and a secondary spine. X 1.8 (p. 435). 



Fig. 6. Keokuk Group, Lower Carboniferous, Warsaw, Illinois. Mus. Comp. Zodl. Coll., 3,070. This is the holotype of 

 Pholidocidaris meeki Jackson, here considered a synonym. X 0.9. Ventral area, the only known specimen of the 

 i showing this area at all satisfactorily. Ambulacral plates are large, each with a central pore-pair There are 

 apparently six columns of ambulacral plates at the mid-zone in an area. In interambulacrum C the primordial 

 iterambulacral plate is in place in the basicoronal row; there are two plates in the second row and three in the third 

 rth column does not originate until the sixth row, which is exceptionally late for any Palaeozoic species- the 

 )lumn originates m the seventh row and the sixth column in the eighth row. Interambulacrum A is confused 

 imperfectly preserved. There is a primary tubercle on all interambulacral plates ventrally, whereas dorsallv 

 s. i, 4) primary tubercles occur only on adradial plates (p. 438). 



Fig. 7. The same specimen, from the area marked X in area C of fig. 1. X 1.8. Ambulacral plates showing their 

 itively large size, ventral imbrication, central pore-pair in an elevated prominence, and interambulacral plates 

 which are scaly, rounded, imbricating dorsally and laterally (p. 438). 



