PLATE 20. 



Echiiiocystites pomum Wyville Thomson. Page 252. 



Figs. 1-4. Lower Ludlow, Silurian, Leintwardine, England. 



Fig. 1. After Wyville Thomson, 1861, Plate 4, fig. 3. Cotype. X 0.9. Ambulacra narrow, the anal area (?) lies dorsally 



in an interambulacral area. Jaws and spines in place. (Compare Plate 16, fig. 4.) 

 Fig. 2. After Wyville Thomson, 1861, adapted from his Plate 4, fig. 2. Cotype. Enlarged. Impression of the exterior 



showing four columns of plates in an ambulacral area and associated interambulaeral plates. 

 Fig. 3. After Wyville Thomson, 1861, Plate 4, fig. 3. Cotype. Much enlarged. A single interambulacral plate with a 



primary and secondary tubercles and a primary spine. 

 Fig. 4. British Museum Coll., E. 1,300. X 3.5. External mold, showing eight columns of plates in an interambulacral 



area, the width of an ambulacrum, also tubercles and spines. 



Koninckocidaris silurica sp. nov. Page 285. 



Fig. 5. Same specimen as photograph, Plate 19, fig. 1. Holotype. X 1.4. About three ambulacral plates equal the height 

 of an interambulacral. Ambulacral plates bevel over the interambulacral and imbricate dorsally, as this is an internal 

 view. Pores are near the middle of the ambulacral area, a usual character of the interior. Eight columns of nearly 

 rhombic interambulacral plates in area A, all of which extend to the apical disc. All interambulacral plates imbricate 

 ventrally and toward the center, nearly covering column 7. This is because it is an internal view. (Compare text- 

 figs. 32-37, p. 75.) An ocular plate is in place capping ambulacrum B and the lateral borders of interambulacra 

 A and C. Two genitals are in place, partially restored in C, as indicated by dotted lines, and a few periproctal plates. 

 A plate between ocular B and genital A may be a displaced periproctal plate. The apical disc is small. 



Fig. 6. Same specimen, ambulacral plates of area J. X 3.6. An elevated T-shaped ridge is on each plate with pores 

 on the ventral side of the same. An X in figs. 5 and 6 indicates the location of the plates figured in each. 



Lepidocentrus rhenanus (Beyrich). Page 288. 



Fig. 7. Devonian, Wippenfurth. Museum fur Naturkunde Coll., Berlin. Holotype. X 0.9. The specimen is an internal 

 mold. Ambulacral plates low, interambulacra with five columns in each area. In area E, the primordial inter- 

 ambulacral plate is in the basicoronal row; there are two plates in the second row, three in the third, and four in the 

 fourth row, the fifth column coming in below the ambitus. Jaws present. 



Lepidocentrus miilleri Schultze. Page 289. 



Fig. 8. Same specimen as photograph, Plate 19, fig. 2. Holotype. X 0.9. Ambulacra narrow, plates low. Inter- 

 ambulacrum A with 11 columns of plates imbricating strongly dorsally and from the center laterally; several of 

 the columns drop out, passing dorsally. 



Fig. 9. Same specimen from the area marked X in fig. 8. X 3.6. Ambulacral plates showing the number against an 

 interambulacral plate, the lateral position of pores and the beveling under interambulacral plates on the left. 



Fig. 10. Same specimen, from the reverse side. X 3.6. Internal impression from near mid-zone. Pores in the center 

 of each plate, ambulacral plates wider than on exterior, and interambulacral more angular than on exterior. 



Fig. 11. Middle Devonian, Pelm, Prussia. Mus. Comp. Zool. Coll., 3,103 (from R. T. J. Coll.). X 1.7. Interambula- 

 cral plate from a left half-area, showing beveling, two primary tubercles with scrobicules and secondary tubercles. 



Fig. 12. Same horizon, locality, and collection. X 1.7. Plate from a right half-area with one primary tubercle, the more 

 usual character. 



Fig. 13. Middle Devonian, Muhlenberg, near Gerolstein, Prussia (after Schultze, 1866, Plate 13, fig. Ib). Enlarged. Am- 

 bulacra narrow, plates low, pore-pairs uniserial and near the interambulacral suture. 



Lepidocentrus eifelianus Muller. Page 291. 



Fig. 14. Devonian, Rommersheim, Prussia (after Muller, 1857, Plate 3, fig. 1). Cotypes. X 0.9. Interambulacral 

 plates showing surface characters and beveling. 



Tornquistellus gracilis (Tornquist). Page 291. 



Fig. 15. Lower Carboniferous, Hunsrucken, Prussia (after Tornquist, 1897, Plate 20, fig. 5). Holotype. X 0.9 and 

 enlarged. Tubercles widely spaced, small primaries with scrobicular rings. 



Fig. 7 from my sketch; figs. 13, 15 copied by W. M. Barrows; all others drawn by J. Henry Blake. 



