PLATE 12. 



Archaeocidaris rossica (Buch). Page 263. 



Figs. 1-13. Lower Carboniferous. Miatschkowa, Province of Moscow, Russia. 



Fig. 1. Mus. Comp. Zool. Coil., 3,086 (from R. T. J. Coll.). X 4. Dorsal view of two half-pyramids with epiphyses, 

 brace, and compass in place; this is the most nearly perfect specimen of a compass seen from the Palaeozoic (p. 182). 



Fig. 2. The same restored. 



Fig. 3. Mus. Comp. Zool. Coll., 3,084 (from R. T. J. Coll.). X 4. Face view of the upper part of two half-pyramids with 

 epiphyses and a brace in place. The space between the half-pyramids, which is occupied by the interpyramidal 

 muscle, is narrower than normal because the half-pyramids are somewhat out of place, compare fig. 5. 



Figs. 4-6. A very fine lantern in the Palaeontological Museum, Munich. 



Fig. 4. Pyramid face view. X 4. Braces and tooth in place, foramen magnum moderately deep. 



Fig. 5. Ventral view. X 4. The pyramids curve laterally, giving spaces for long interpyramidal muscles, the lantern 



is strongly inclined, as is obvious from the amount of the pyramids seen from this view. 

 Fig. 6. The same specimen, dorsal view. X 4. Epiphyses, braces, and teeth in place, the foramina magna moderately 



deep. (Figs. 4-6, compare text-fig. 208, p. 184.) 

 Fig. 7. Mus. Comp. Zool. Coll., 3,085 (from R. T. J. Coll.). Upper part of two half-pyramids, in sidewise view. X 4. 



Epiphyses, brace, and tooth in place; p.s., pyramidal suture. 

 Fig. 8. Mus. Comp. Zool. Coll., 3,086 (from R. T. J. Coll.). X 4. Pyramid, side view, showing ridges for the attachment 



of interpyramidal muscle, epiphysis with glenoid cavity, a displaced brace, and a tooth, the latter restored ventrally, 



as indicated by dotted lines. 

 Fig. 9. Mus. Comp. Zool. Coll., 3,087 (from R. T. J. Coll.). X 8. Ambulacral plates with an adjacent adradial plate. 



The ambulacral plates bevel strongly under the adradials as seen on the right. On the left the ambulacrum is pushed 



out of place under the adradial plate. Outline of ambulacrum undulate, conforming to the outline of the interambula- 



crum. (Compare Plate 10, fig. 10.) 



Fig. 10. The same, ambulacral plate, in side view to show the adradial bevel. X 4. 

 Fig. 11. Mus. Comp. Zool. Coll., 3,084 (from R. T. J. Coll.). X 4. A plate not in place, perhaps a genital, seen from the 



interior. 

 Fig. 12. Mus. Comp. Zool. Coll., 3,087 (from R. T. J. Coll.). Natural size. Test, ventral view. The limit of the upper 



part of the figure is about on the line of the ambitus. 

 Fig. 13. Mus. Comp. Zool. Coll., 3,091. Natural size. Primary spines, showing their form and spinules. (Compare 



Plate 11, fig. 5.) 



Figs. 1-3 and 7-11 drawn by J. Henry Blake; figs. 4-6 drawn by Anton Birkmaier; photographs by F. A. Saunderson. 



