456 ROBERT TRACY JACKSON ON ECHINI. 



*Xenocidaris cylindrica Schultze. 

 Text-fig. 255, p. 455. 



Xenocidarw cylindrica Schultze, 1866, p. 126, Plate 13, figs. 4-4c: Loven, 1874, p. 42; Klem, 1904, p. 76; 

 Lambert and Thiery, 1910, p. 126. 



The spines are not cylindrical as the name implies, but spindle-shaped, thickly set .with 

 small nodose spinules, which are quite regularly spaced. A spine in the Munich Museum 

 measures 55 mm. in length. In the British Museum there are six fragmentary spines, E 10,693 

 to E 10,698. One of these, E 10,693, is 28 mm. long, incomplete distally, but proximally has 

 an expanded milled ring, which is angular in outline, with the milling nearly worn off, and 

 resembling the base of the spines of Archaeocidaris rossica (Plate 12, figs. 13a-13k). The base 

 of the spine is hollowed for articulation with a tubercle of considerable size. This specimen is 

 important, as it is the only one I know of in the genus which shows the proximal end of the 

 spine. The structure shows that it is typically echinoid, a fact that was not definitely known 

 before. The character of the spines strongly suggests that of Archaeocidaris, but, as that genus 

 has not yet been recorded from the Devonian, it is probably best to leave the species in its 

 present genus, awaiting further knowledge. 



Middle Devonian, Gerolstein, Prussia, cotypes (five spines) from the Schultze Collection, 

 Museum of Comparative Zoology Collection 3,201; British Museum Collection E 10,693 to 

 E 10,698; Munich Museum. 



NOMINA NUDA. 



Archaeocidaris tirolensis Stache, 1876, p. 260; Klem, 1904, p. 64; Lambert and Thiery, 1910, p. 125. 

 No description of this species has been published. 



Echinocrinus cidariformis (?) T. and T. Austin, 1842, p. 111. 

 No description of this species has been published. 



Echinocrinus pomum T. and T. Austin, 1842, p. Ill; 1843, p. 207. 



The species Echinocrinus pomum, though not described, is discussed under the consid- 

 eration of Echinocrinus anceps by the Austins (1843). (Seep. 449.) 



HETEROCIDARIS Hall; Heterocidaris keokuk Hall; Heterocidaris laevispina Hall. 



Miller in his Catalogue of North American Fossils (1897, p. 747) gives the names of the 

 genus Heterocidaris with the two species as listed, and attributes them to Hall's (1861) 

 " Descriptions of New Species of Crinoidea from Investigations of the Iowa Geological 

 Survey." Hall's paper consists of 18 pages in the copies I have seen, but there is a rumor 



