REVISION OF PALEOZOIC STELLEEOIDEA. 



95 



"^w 



Fig. 8. — Spanuster latiscutatus, aftee 

 Sch5ndorf. Schematic arrangement of 



THE ABACTINAL PLATES. a, PRESUMABLE 



POSITION OF anus; Ce, central plate; 

 Jri, BASAL interradlillv; indp, probable 



POSITION OF MADREPORITE; mo, SUPRAMAR- 

 GINALLV; -Ri, BASAL KADLiLIA. 



thickened in the center and greatly depressed to the sutures. Thus each 

 plate has a cushioned surface. Between the ends of each plate of the 

 middle row are two minute accessory plates lying in the angles at 

 which the lateral plates enter. At the base of each ray and upon the 

 disk is a single large plate whose surface rises into a high clavate node. 

 Between each two of these is one of 

 less height. The central portion of 

 the aboral area is destroyed and no 

 trace of madrepore is seen. 



''The width of tliis specimen from 

 tip to tip is 33 mm, 



"Occurrence: Jennings formation, 

 Chemung member? Yellow sandstone 

 on the road northeast of Oakland, 

 Gan-ett County [Maryland], where it 

 is associated ^vith Spirifer disjunctus. 



"Collection: Maryland Geological 

 Survey." 



Remarks. — This clearly determined 

 species is a late survival of early 

 Paleozoic primitive asterids. The 

 characters so far as determinable in 

 the natural mold are those of Meso- 

 palseaster, but as the disk skeleton is not preserved, it is very prob- 

 able that when this feature is known the form will be seen to belong 

 to a new genus. 



Genus SPANIASTER Schondorf. 

 Plate 12, figa. 1, 2; text fig. 8. 

 Coelaster Sandbkrger (not Agassiz 1835), Verst. d. rheinischen Schicht. Nassau, 



1855, p. 381. 

 Spaniasler Schondorf, Jahrb. nassauisch. Ver. Naturk., Wiesbaden, vol. 60, 

 1907, p. 176; vol. 62, 1909, p. 30; Palaeontographica, vol. 56, 1909, pp. 73, 109. 



Remarks. — This genus with its single very small species has its 

 nearest relations with Ilesopdlseaster, in that it has a single axillary 

 interbracliial plate in each actmal axillary area, but differs from it 

 in that there are many more adambulacral and ambulacral plates 

 than there are inframargmals. The marked and generic difference, 

 however, is on the abactinal side, where there are but three columns 

 of plates, one radial and two suuramarginal, of large and thick ossicles 

 arranged in parallel rows, the pieces of which do not alternate vdih 

 one another; further, the supramarginals are almost completely 

 superposed upon the inframarginals, the two columns together, but 

 more particularly the inframarginals, boundmg the rays and not the 

 inframarginals alone, and not so pronouncedly as in Mesopalxaster. 

 The disk is also more primitive m its construction, in that the central 



50G01»— Bull. 88 — 15 7 



