PLATE 25. 



Hyattechinus pentagonus sp. nov. Page 295. 



Figs. 1-4. Waverly Group, Lower Carboniferous, Meadville, Pennsylvania; all external sandstone molds. 



Fig. 1. Mus. Comp. Zool. Coll., 3,107 (from R. T. J. Coll.). Paratype. X 1.8. External mold of the ventral side, the 

 same specimen as photograph, Plate 24, fig. 4. Ambulacra broad, petaloid; pore-pairs uniserial with clearly defined 

 peripodia. Interambulacra in each area have the primordial plate in the basicoronal row; there are two plates in 

 the second row and three plates in the third row, dorsal to which new columns are added with great rapidity, indi- 

 cating a very accelerated development, eleven columns being attained before reaching the ambitus. The peristome, 

 as far as preserved, has ambulacral plates only. The plates are partially restored in areas D and E, as indicated 

 by dotted lines. 



Fig. 2. Same specimen. X 7. Enlarged to show detail of ambulacral plates. Pore-pairs in peripodia from the area 

 marked X in fig. 1. 



Fig. 3. Alleghany College Coll. Holotype. X 1.8. Dorsal view. Same specimen as photograph, Plate 24, fig. 1. Am- 

 bulacra narrow, marking the limits of the pentagon radially. Interambulacra with 14 columns of plates in each 

 area, the highest number known in any sea-urchin. The 13th and 14th columns originate above the ambitus. In 

 area C there are only four plates in column 14. Columns 1 and 2 and some additional columns drop out before reach- 

 ing the apical disc. Four of the genital and ocular plates and a few periproctal plates are in place dorsally. The 

 apica t l disc is small, measuring proportionately about 16 % of the diameter of the test. Remarkably clear for a 

 sandstone mold. 



Fig. 4. Same specimen. Holotype. X 3.6. Enlargement to show the dorsal structure of one interambulacrum. Col- 

 umns 1, 2, 10, and 13 drop out before reaching apical disc. 



Hyattechinus beecheri sp. nov. Page 297. 



Fig. 5. Yale Mus. Coll., 323. Same specimen as photograph, Plate 24, fig. 8 and Plate 26, fig. 1. Holotype. X 3.6. 

 Shows genital, ocular, and periproctal plates. The oculars and in part the genital and periproctal plates are restored, 

 as indicated by dotted lines. All of these plates are represented by impressions only as the specimen is an internal 

 sandstone mold. The genital pores are not indicated as they were not seen in the specimen. 



Figs. 3 and 4 drawn by J. H. Emerton; figs. 1, 2, 5 by J. Henry Blake. 



