REVISION OF PALEOZOIC STELLEKOIDEA. 93 



Interbrachial arcjis with single, large, hexagonal, axillary inter- 

 brachial plates. 



Adambiilacral pieces quadrangular, fairly uniform m size for two- 

 thkds the length of the rays and then become grackially smaller 

 distally; there are about 15 in a column. A peculiarity of this 

 species is that the ambulacralia do not contmue around the axillary 

 interbrachials, but cease with the basal inframarginals. There are, 

 therefore, m M. caradaci no adambulacral oral armature pieces. 



Ambulacral furrows moderately wid(;, with as many rectangular 

 ambulacralia as there are adambulacrals, plus probably four more 

 in each column, and these contmue around the axillary interbrachial. 

 Therefore, the oral armature consists entirely of ambulacraha. All 

 of these ossicles are directly opposite one another and have high 

 medial crests that are contmuous across the ambulacral furrow. 

 Podial openings large laterally between the plates and the adambu- 

 lacrals. 



Locality and formation. — Caradoc sandstone, Soudle}^ quarry. 

 Church Stretton, England. The holotype, a spUt nodule, is in the 

 British Museum (Natural History), No. 48206; wax squeezes from 

 wliich the photographs have been made are in the United States 

 National i\Iuseum. Other specimens, Bather states, are in the Museum 

 of Practical Geology, London; these are from Marshbrook and occur 

 at a somewhat higher geological level. 



Remarks. — Gregory wi-ote in 1899 that "the nearest ally of tliis 

 species is P. matutina (Hall)," but the illustrations here presented 

 wiU show that the relationship is Avith Mesopalseaster shafferi and not 

 with Hudsonaster matutinus. 



Cat. No. 60606, U.S.N.M. 



MESOPALiEASTER (?) ACUMINATUS (Simonovltsch). 



Asterias acuminatus Simonovitsch, Sitzb. d. mat.-naturw. Olasse Akad. Wiss., 



Wien, vol. 64, Abt. 1, 1871, p. 100, pi. 3, figs. 2-2d. 

 Asterias acummata Schondorf, Pateoiitographica, vol. 56, 1909, pp. 72, 109, 



pi. 11, figs. 7, 8. — Schondorf, Jahrb. nassauisch. Ver. Natiirk., Wiesbaden, 



vol. 62, 1909, p. 32, pi. 5, figs. 4, 5. 

 Roemerastcr (f) acuminatus Sturtz, N. Jahrb. fiir Min., etc., 1886, vol. 2, p. 154. 



Actinally tliis small and slender species is nearly in harmony with the 

 generic characters of Palscaster and Hudsonaster, differing only in that 

 the axiUary interbrachial plates barely extend to the margin of the 

 disk, while in those genera they are prominent and marginal in the 

 axils. In Asterias acuminatus they arc as yet not crowded so far orally 

 as in most species of Mesopalseaster. It is a difference of degree, not 

 of land; therefore this species has more the actinnl character of 

 Mesojpalaeaster than Hudsonaster. Ambulacral plates unknown. 



Abactinally Simonovitsch's species is said to have six colunnis of 

 tumid plates, all alike and persisting throughout the rays. If the 



