PLATE 11. 

 Archaeocidaris rossica (Buch). Page 263. 



Figs. 1-5. Lower Carboniferous, Miatschkowa, Province of Moscow, Russia. 



Fig. 1 Ventral view of a nearly perfect specimen. Diameter through A. F, 46 mm. Palaeontological Museum, Munich. 

 X 2. Ambulacra are best preserved in areas H and J. four columns of plates in each interambulacral area. Inter- 

 ambulacral plates are higher than wide, increasing in height to the ambitus. Basal terrace moderately strong, with 

 large scrobicular area (seen better in fig. 4); the flange bearing secondary tubercles, is wider in the ventral and dorsal 

 portion of each plate. On the peristome there are many small scale-like imbricating ambulacral and interradial non- 

 ambulacral plates. 



Fig. 2. Same specimen, dorsal view. X 2. Interambulacral plates are much higher than ventrally, the basal terrace is 

 wanting dorsally, although the tubercles are well developed still further dorsally as seen in a plate in column 3 of area ( ', 

 the young tubercle is imperforate, as in young tubercles of recent Cidaridae, Plate 3, figs. 1, 2. In the youngest 

 interambulacral plates, seen best in area 1, no tubercle is yet developed. Within the center are many small peri- 

 proctal plates. This, which is shown spread out on the Loven method in Plate 10, fig. 10, is the most complete speci- 

 men known in the genus. 



Fig. 3. The same. X 8. Enlargement of periproctal plates; the two larger plates are possibly ocular and genital, from 

 area D of fig. 2. 



Fig. 4. Interambulacral plate showing perforate mamelon, sunken platform, with its elevated ring-like parapet, the 

 boss bounded by the basal terrace, and a rather wide scrobicule within the scrobicular circle. On the margin of the 

 plate are secondary and miliary tubercles. Secondary spines are vertically finely striate and miliary spines are in place; 

 these are the only miliary spines so far known in specimens of the genus Mus. Comp. Zool. Coll., 3,088 (from R. T 

 .). Coll.). X 4. " 



Fig 5. Base of primary spine, showing milled ring, fine vertical striation, and nodose spinules. Mus. Comp. Zool Coll., 

 3,091 (from R. T. J. Coll.). X 4. (Compare Plate 12. figs. 13a-13k.) 



Figs. 1-3 drawn by Anton Birkmaier; figs. 4, 5 drawn by J. Henry Blake. 



