256 ROBERT TRACY JACKSON ON ECHINI. 



of a different species; but if one were to maintain that it came merely from a different part of 

 the test of C. laevispina, I do not see how it could be disproved." 



Sandberger's material all came from the Middle Devonian, Stringocephalus Limestone 

 of Villmar, and is in the Wiesbaden Museum as above noted. Two interambulacral plates 

 from the Devonian of Villmar are in the Museum of Comparative Zoology 3,192, from the 

 Schiiltze Collection. 



Archaeocidaris M'Coy. 



Echinocrinm L. Agassiz, 1841, p. 15; Bather, 1907; 1909; 1909a, p. 264. 



Archaeocidaris M'Coy Mss., 1844, p. 173; M'Coy, 1849, p. 252; Young, 1873; 1876; Loven, 1874, p. 43; 



Duncan, 1889a, p. 11; A. Agassiz, 1881, pp. 79, 80; Lambert and Thiery, 1910, p. 124. 

 Palaeocidaris L. Agassiz and Desor, 1846-'47, p. 340. 

 Cidarotropus Pomel, 18S3, p. 113; Lambert and Thiery, 1910, p. 125. 

 Permocidaris (pars) Lambert, 1899a, pp. 39, 47; Lambert and Thiery, 1910, p. 127. 



The test is depressed spheroidal, ambulacra narrow, sinuous in outline, conforming to 

 the outline of the massive adradial plates. Ambulacral plates are low, of uniform character, 

 imbricating moderately adorally and beveled strongly under the adradials; the pore-pairs 

 are uniserial. Interambulacra, in all species where a fairly complete test is known, with four 

 columns of plates in each interambulacral area. The adradial plates are pentagonal, but 

 rounded on the adradial suture line; plates of the intermediate columns are hexagonal. Each 

 plate bears a prominent perforate median tubercle with a wide scrobicular area and a basal 

 terrace, though this terrace, being a slight feature, may be worn off in eroded plates and is 

 absent {A. rossica) in young plates dorsally. 



Beyond the border of the scrobicular circle are secondary tubercles which differ in their 

 number and in the extent of surface which they cover both in different species and somewhat 

 in plates of different parts of the test in the same species (A. rossica). Primary spines are 

 relatively large, often very large, with a concave base, marked milled ring, and a shaft tapering 

 or enlarged, smooth or ornamented with striations, spinules, or rarely flange-like vertical ridges. 

 The primordial ambulacral plates are on the peristome around the mouth, and the primordial 

 interambulacral plates with additional rows are resorbed in the advance of the peristome, as 

 there are four plates in the basicoronal row (Plate 9, figs. 7, 8). The peristome is covered with 

 radially situated ambulacral and interradially situated non-anibulacral plates, all small and 

 imbricating adorally (text-fig. 47, p. SO). Ocular and genital plates are doubtful, periproct 

 with many small angular plates. The lantern is well developed, of the typical Palaeozoic 

 character (Plate 12, figs. 1-8). Of this genus a few species are known fairly completely,' but 

 there are numerous species described from incomplete material, often only one or more dis- 



' The best known species, especially as regards the test, are Archaeocidaris worlheni, legrandensis, rossica, agassizi, and 

 urii. 



