454 ROBERT TRACY JACKSON ON ECHINI. 



Protoechinus anceps T. Austin. 



Protoechinun nmrps T. Austin, 1860, p. 446, text-fig.; Love'n, 1874, p. 42. Klem, 1904, p. 75. 

 Proto Echinus - - Baily, 1865c, p. 66. 

 Melonechinta anceps I/ambert and Thiery, 1910, p. 120. 



With characters of the genus. This looks like a very interesting type, but with present 

 knowledge cannot be definitely located. The ambulacrum passing from two columns of 

 primary plates to four columns in an area, as figured by Austin, suggests the development of 

 an ambulacral area as seen in the Palaeechinidae. Two ambulacral plates equal the height 

 of an adradial. The interambulacrum is represented only by an adradial column as figured 

 by Austin. T. and T. Austin earlier (1842) gave the name Echinocrinus anceps to a distinct 

 species; as both are very little known, there is a possibility of confusing these names (p. 449). 



Lower Beds of the Carboniferous Limestone, Hook Point, County Wexford, Ireland. 



Rhoechinus sp. Duncan. 



Rhoechinus sp. Duncan, 1889, p. 205; Klem, 1904, p. 30. 



Duncan states that the specimen is small and in the Woodwardian [now called Sedgwick] 

 Museum at Cambridge, England. Since he used Rhoechinus for Palaeechinus as here con- 

 sidered (p. 303), this specimen is probably a species of Palaeechinus. 



Rhoechinus (?) sp. Tornquist. 



Rhoechinus (?) sp. Tornquist, 1897, p. 763, Plate 20, fig. 8; Klem, 1904, p. 30. 



Tornquist figures only an imperfect plate. Genus quite unrecognizable, but Tornquist 

 uses the generic name Rhoechinus for Palaeechinus as here considered (p. 303). 



XENOCIDARIS Schultze. 



Xenocidaris Schultze, 1866, p. 126; Loven, 1874, p. 44; Lambert and Thiery, 1910, p. 12(i. 

 Eocidaris (pars) Pomel, 1883, p. 113. 



This genus was based on peculiar spines from the Devonian of the Eifel region, which are 

 not even yet found in association with a test or plates. The base of the spines is known only 

 in a specimen of X. cylindrica as described below. Here the spine has a milled ring and con- 

 cave base for articulation with a tubercle of considerable size. The spines are doubtless refer- 

 able to Echini, and quite possibly to the Cidaroida (pp. 245, 455) but as plates of the tost arc 

 as yet unknown it seems safest to treat of the genus and species here. 



Type species, Xenocidaris clavigera Schultze, from the Devonian, of Prussia. 



