REVISION OF PALEOZOIC STELLEROIDEA. 297 



PLATE 24. 



FIGS. 1-2. Xenaster margaritatus Simonovitsch. 



1. Reconstruction, somewhat enlarged, of the abactinal side. The 

 structure of the medial portion of the disk is based upon Agalmaster 

 miellensis. 



2. Reconstruction, somewhat enlarged, of the actinal area. 

 After Schondorf. 



* Lower Devonic (Upper Coblenzian). Niederlahnstein, Germany. 



PLATE 25. 



FIG. 1. Promopalssaster dyeri (Meek) (also see plates 18 and 20). 



Retouched photograph, natural size, of the actinal side of the holotype. 



Upper Ordovicic (Maysvillian). Cincinnati, Ohio. 



Dyer collection, Museum of Comparative Zoology, Harvard University 

 (No. 13). 

 FIG. 2. Lepidasterella babcocki, new species. 



Photograph X 1.5 of the holotype. A natural mold of the abactinal 

 area in sandstone. 



Upper Devonic (Lower Chemung). Near Ithaca, New York. 



Collection of Mrs. G. W. Babcock. 



PLATE 26. 



FIG. 1. Petraster spedosus (Miller and Dyer) (also see plates 23 and 27). 



Retouched photograph, natural size, of the abactinal area of the holotype. 



Upper Ordovicic (Richmondian). Near Winchester, Ohio. 



Dyer collection of the Museum of Comparative Zoology, Harvard Uni- 

 versity (No. 14). 

 FIG. 2. Petraster (?) americanus (D'Orbigny). 



Reproduction, natural size, of Meek's original figure. The specimen is 

 seen from the abactinal side, exposing, however, the inner surface of the 

 actinal skeleton, which is deeply embedded in limestone. 



Upper Ordovicic (Maysvillian). Cincinnati, Ohio. 



Collection of the University of Chicago. 



PLATE 27. 



FIGS. 1-4. Petraster spedosus (Miller and Dyer) (also see plates 23 and 26). 



1. Camera lucida drawing X 4 of the abactinal side of a ray. Holotype 

 The inframarginals border the animal, with the supramarginals imme- 

 diately inside of them. The radial column is readily distinguished 

 along the center of the rays. 



2. Camera lucida drawing X 6 of an interbrachial area in a young 

 individual (Harris collection, Cat. No. 60609, U.S.N.M.). The inframar- 

 marginals are above and the adambulacrals below to the right. The rest 

 rest of the plates are accessory interbrachials. 



3-4. Madreporite from the side and from the lower or under surface, X 8. 

 FIG. 5. Petraster rigidus (Billings). 



Outline tracing of the actinal skeleton from a photograph X 2 of the 

 holotype. 



Middle Ordovicic (Trenton). Ottawa, Canada. 

 Collection of the Geological Survey of Canada (No. 1401a). 



