98 BULLETIN 88, UNITED STATES NATIONAL MUSEUM. 



Axillary interbrachial plates large, a single one situated in each 

 area between the adambulacral and inframarginal columns. Each 

 bears short, thick, blunt spines. 



Mouth plates (tori) minute, one situated in front of each pair of 

 oral armature plates. 



Genoholotype. — Palseaster eucharis Hall. 



Distribution. — Restricted to the Hamilton and Chemung of the 

 American Devonic. The species are: 

 D. eucharis (Hall). Hamilton. 

 D. chemungensis, new species. Chemung. 



RemarJcs. — This genus is readily distinguished from Hudsonaster 

 in having well-developed radial and ambital accessory plates, in 

 the numerous very small plates of the disk and in the presence of 

 mterbrachial axillary plates. 



Devonaster differs from Palseaster in having radial columns of 

 plates and in the presence of three plates in each interbrachial area 

 against one in Palxaster. There are also other differences. From 

 Neopalseaster it differs in having ambital accessory plates and no 

 ocular plates; while the proximal supramarginals and radials are 

 very large in the former, they are small in Devonaster, particularly 

 the supramarginals, which are not readily distinguished from the 

 accessory disk plates. In Mesopalaeaster and Promopalxaster the 

 accessory plates are always arranged in columns or rows and the 

 ambital accessory plates are not restricted to the axillary areas as 

 in Devonaster. Further, in those genera (excepting in the smaller 

 forms of Mesopalxaster) there are always from two to five inter- 

 brachial marginal plates, while Devonaster has but one axillary 

 marginal in each interbrachial area. 



Devonaster greatly resembles abactinally Xenaster of the Lower 

 Devonic of Germany, but is readily distinguished actinally in that 

 the latter has more large interbrachial plates, and especially in the ad- 

 dition of numerous accessory interbrachial pieces. These differences 

 are pointed out m more detail in the remarks on Xenaster. 



DEVONASTER EUCHARIS (Hall). 

 Plate 12, figs. 3-5. 



Palseaster eucharis Hall, Twentieth Rep. N. Y. State Cab. Nat. Hist., 1868, p. 

 287, pi. 9, figs. 3-3a (?4); rev. ed., 1868=1870, p. 330, pi. 9, figs. 3-3a (?4).— 

 QuENSTEDT, Petrefactenkunde Deutschlands, vol. 4, 1876, p. 71, pi. 92, 

 fig. 29.— ZiTTEL, Handb. Pal., vol. 1, 1879, p. 452, fig. 323.— Cole, Bull. 

 Geol. Soc. America, vol. 3, 1892, p. 512, pi. 15.— Clarke, Bull. N. Y. State 

 Mus., No. 158, 1912, pp. 44-45, 6 pis. 



Xenaster eucharis Schondorf, Jahi-b. nassauisch. Ver. Natui-k., Wiesbaden, vol. 

 66, 1913, pp. 87-96, pi. 3, figs. 1, 2, text figs. 1-3. 



Original description. — "Body rather large; the largest individual 

 being one inch and seven-eighths from the center of the body to the 

 extremities of the rays; the whole having a robust aspect; rays 



