INSERTAE SEDIS 445 



ber of basals to the characters given by all previous authors could not have been supported 

 by more satisfactory evidence of the facts, — the more so since these statements have since 

 been incorporated with the description of E. pocilliformis in the volume on the Lower 

 Devonian, of the Reports of the Maryland Geological Survey, 1913, p. 257. Notwithstand- 

 ing the definite statements above quoted as to certain specimens being dicyclic and showing 

 infrabasals, I must say that the corresponding figures on plate 4 of the author's paper fail 

 to show any means of determining the number of plates below the radials, or any indication 

 of two rings of such plates, or in fact any structures essentially different from those shown 

 by Hall's figures 8-12 on plate 5 of the New York Report, on which he based the statement 

 in his description, — " base solid, without division of plates " ; or those which 1 have seen in 

 hundreds of specimens of the fused bases from New York, Maryland, Virginia and Ten- 

 nessee. The raised collar on some specimens, which the author took to represent basals, 

 distinguishable from the narrower mass below it thought to be infrabasals, is a mere irregu- 

 lar phase of secondary growth without definite structure, seen occasionally on specimens of 

 different species. Also the lines seen at the inner surface of some of the fused bases are not 

 interbasal sutures, as the author thought, but are lines or ridges marking the position of the 

 superimposed radials and anal plate ; they are always 6 in number, instead of 5 as they 

 would be if dividing five basals (see Hall, op. cit., pi. 5, fig. 12 ; pi. 87, fig. 14 ; and PL LXXVI, 

 figs. 3, 16, 18 herein, in which both the ridges and the true suture lines are shown). 



Dr. Kirk, the latest author to discuss the characters of Edriocrinus, 1 follows substan- 

 tially the definition of Hall, saying that — 



The cup consists of five radials and an anal plate .... This cup rests upon an apparently amorphous 

 base (p. 112) .... This base for purposes of convenience I have styled a peduncle (p. in). 



As against these recent interpretations of the structure of the genus, I am now in posi- 

 tion definitely to show by unquestionable evidence in four species that Edriocrinus is a 

 monocyclic crinoid with 4 basals, as in Mclocrinus and associated genera: 



1. A rather small species, occurring only in the form of the fused basals somewhat 

 abundantly in the Linden formation of the Helderbergian of western Tennessee, and in 

 equivalent New Scotland beds of Virginia. As usually found in cherts or clay layers the 

 specimens are silicified, and the rounded base is altered by secondary growth to an undiffer- 

 entiated, more or less elongate, fused bulb, and all sutures at the surfaces are completely 

 obliterated by growth or by silicification. Rarely the wall appears double, with an inter- 

 mediate space that was filled with some fibrous matter now decomposed ; and in one such 

 specimen the original interbasal suture lines are marked by silicious partitions, by which the 

 position of the 4 basals is distinctly shown (PI. LXXVI, fig. 12). Defining species by means 

 of the fused basals alone is rather unsatisfactory, as there is. some variation among associ- 

 ated specimens ; yet in the absence of better material this course seems advisable, in order to 

 have names for some of the forms having rather characteristic facies as evidenced by the 

 average form and proportions in a number of specimens. To this form I have given the name 

 Edriocrinus occidentalis (PI. LXXVI, figs. 6-12). 



2. At a locality in the typical Linden limestone and shale beds in Perry County, Ten- 

 nessee, a much smaller species occurs, in which the consolidated base is calcareous and the 

 sutures are still visible, although sometimes partly obscured by growth, and indistinct or 

 " ragged " at the surface. In such cases by grinding or scraping, the sutures can usually be 

 found a short distance inward. I have nine specimen's in which the sutures are perfectly 

 plain, showing 4 basals in every case. This form, in which I first identified the 4 basals, 

 may be called Edriocrinus explicatus (PI. LXXVI, figs. 13-15). 



1 Proc. U. S. Nat. Mus., vol. 41, 1911, pp. 112-114. 



