246 



ROBERT TRACY JACKSON ON ECHINI. 



Eocidaris venieuiliana Desor, 1858, p. 156, Plate 21, figs. 13, 14; Loven, 1874, p. 43. 



Eocidaris keyserlingi Geinitz, 1861, p. 108, Plate 20, figs. 5-9; Loven, 1874, p. 42 ; Klem, 1904, p. 68. 



Eocidaris kaiscrlingi Kolesch, 1887, Plate 38, figs. 1-27; Doderlein, 1887, p. 39, Plate 11, fig. 8; Spandel, 



1898, p. 33, Plate 13, figs. 1-6. 

 Eotiaris keyserlingi Lambert, 1899, p. 82; Lambert and Thiery, 1910, p. 128. 

 Permocidaris venicuili Lambert, 1899a, pp. 39, 47. 

 Eocidaris vcrneuiliatius Klem, 1904, p. 70. 



Miocidaris keyserlingi Bather, 1909, p. .54, text-figs. 2, 3, Plate 1, figs. 6-17; 1909a, p. 86. 

 Eocidaris rerneuilli Lambert and Thiery, 1910, p. 126. 



This important species has recently received critical consideration from Dr. Bather. The 

 test is small, low, subspheroidal. Ambulacra unknown, but crenulations on the adradial 

 suture face of the interambulacral plates indicate that about four ambulacral plates equal the 

 height of an interambulacral (text-fig. 238 bis). Two columns of relatively high pentagonal 

 plates in each interambulacral area, beveled over the ambulacrals on the adradial suture. The 

 tubercles are prominent, crenulate, with large scrobicules and numerous secondary tubercles 

 on the extra-scrobicular surface. Bather shows that there are low but clearly developed 



238 



238 bis 



Magnesian Limestone, Permian, Tunstall Hill, County 



Text-figs. 238, 238 his. — Miocidaris keyserlingi (Geinitz). 

 Durham, England. 



238. One of the most perfectly preserved specimens of an interambulacrum, showing the association and general 

 shape of the plates. The scrobicules are confluent. X6. (After Bather, 1909, te.xt-fig. 2, p. .58.) 



238 bis. Greater part of an interambulacrum, interior view, showing beveled sutures, denticulation of adambula- 

 eral margin and apophyses of perignathic girdle. (After Bather, 1909, Plate 1, fig. 9.) 



apophyses on the basicoronal plates, as seen from the interior of the test (text-fig. 238 bis). 

 These are the only such structures known in the Palaeozoic (p. 190). The fragment of a test 

 in the Dresden Museum (Plate 9, fig. 2), which is one of Geinitz's original specimens, consists 

 of six plates and measures 5.3 mm. in width. 



The primary spines are up to about 8 mm. in length, above the lower part with small 



