LEPIDOCENTRUS. 289 



The plates of the interambulacra are marked as impressions, the outlines of which are largely 

 ill defined. There are apparently nine columns of plates in each area, as shown in Plate 21, 

 fig. 1. The spines are marked as depressions or elevations in the shale; they are elongate and 

 slender, acicular, and the clearest impressions are about 8 mm. long. 



In the shaly sandstones of the Chemung Group, Upper Devonian, Dryden, Tompkins 

 County, New York; holotype and only known specimens (on a single slab) in the New 

 York State Museum Collection 4,200. 



This species is geologically the oldest known sea-urchin from America, except the Konincko- 

 cidaris silurica herein described. It is not strange that this species has not been figured before, 

 as it is not easy to make out. Professor John M. Clarke kindly sent me the specimen for study, 

 and after careful examination I feel that it should be referred to Lepidocentrus. It certainly 

 has no relation to Archaeocidaris, and does fit in with the characters of Lepidocentrus. As 

 regards the characters of tubercles and spines, primary and secondary, nothing can be definitely 

 said except that the larger spines would compare well enough with the larger spines of Lepido- 

 centrus. 



*Lepidocentrus mUlleri Schultze. 

 Plate 19, figs. 2-5; Plate 20, figs. 8-13. 



Lepidocentrus mulleri Schultze, 1866, p. 124, Plate 13, figs. 1-lf; Loven, 1874, p. 40; Jackson, 1896, 



p. 223, text-fig. 2; Klem, 1904, p. 17. 

 Lepidocentrus mulleri Lambert and Thiery, 1910, p. 122. 



Test spheroidal as gathered from the upper part, which alone is preserved. Ambulacra 

 at the lower part of the type specimen about 5 mm. wide; interambulacrum about 65 mm. wide. 

 This would give a circumference of about 350 mm. and diameter of about 111 mm. The ambula- 

 cra are narrow, plates imbricating ventrally, and strongly beveled under the adradials. The 

 ambulacra, on account of this bevel, are much wider on the interior of the test than on the 

 exterior, as seen by comparing Plate 20, figs. 9, 10. The pore-pairs on the exterior lie near the 

 adradial plates, but proximally are in about the middle of each ambulacral plate. Interambula- 

 cra are broad, with eleven columns, as shown in Plate 20, fig. 8, area A, the only complete area 

 known; but in area C, of the same figure, there are apparently only ten columns. In area A 

 many columns drop out passing dorsally, namely, columns 6, 5, 11, 10, 9, and in the sequence 

 stated. This is a very marked character, indicating reversion or senescence. In my earlier 

 paper (1896, p. 223) this dropping out of columns was by error taken for the coming in of 

 columns, with the result that I oriented the specimen incorrectly, and also incorrectly stated 

 the direction of imbrication (p. 76). The interambulacral plates are thin, nearly rhombic in 

 outline, and imbricate strongly aborally (not orally as I stated before), and from the center 

 outward and over the ambulacra. The beveled edges are shown well in Plate 20, figs. 11, 12. 



