346 SMITHSONIAN INSTITUTION 



which are often large, erect, and form part of the calyx wall ; this also represents a more 

 primitive stage, judging by analogy from the development of the basals in the existing 

 crinoids. The position of the radianal is a thoroughly diagnostic character, by which the 

 genus is sharply differentiated as a homogeneous unit. In addition to Gotland, the genus 

 has now been found in five localities in America, two in the Ordovician, two in the Silurian, 

 and one in the earliest Devonian. Eight species are recognized, which may be arranged as 

 follows : 



The Species of Protaxocrinus 



I. Br with smooth lateral margins. 

 IBB large and erect. 



Br angular at dorsal side. 



IIBr 5 P. elegans. 



Br evenly rounded. 

 Br short and wide. 



Crown rather robust. Anal tube strong. 



IIBr 3 or 4, exceptionally 5 P. laevis 



Br more elongate. 



Crown slender. Anal tube narrow. 



IIBr 5 or 6, exceptionally 4 P. girardeau 



IBB low usually slightly exposed beyond column. 

 IIBr 3. 

 Br evenly rounded. 



Arms heavy, tapering little P. robustus. 



Arms more slender, tapering rapidly P. virginiensis. 



II. Br with angular buttresses at lateral margins. 

 Lateral margins sharply angular. 



Arms ornamented with longitudinal ridges. 



IIBr 4 or more P. interbrachiatus. 



Arms smooth. 



IIBr 4 P. ovalis. 



Lateral margins but slightly angular or smooth. 



Arms ornamented with small nodes. 



IIBr 3 P. salteri. 



Protaxocrinus elegans (Billings) 

 Plate XLV, fig. 1 



Lecanocrinus elegans Billings, Rep. Geol. Surv. Canada, 1853-56 [1857], p. 278; Geol. Surv. Canada (Can. 



Organ. Remains), Decade IV, 1859, P- 47, p'- 4> figs. 40, b. 

 Taxocrinus elegans, Wachsmuth and Springer, Revision Palaeocrinoidea, pt. 3, 1886, pp. 144, 201 ; 



Springer, Jour. Geology, XIV, 1906, p. 487. 

 Protaxocrinus elegans, Springer, Geol. Surv. Canada, Mem. No. 15P, 1911, p. 11. 



A relatively large species. Crown elongate, with long, slender arms, widest 

 about the upper IIBr. Rays prominent, angular at dorsal side, with lateral 

 margins straight. iBr areas depressed. Calyx narrow, height to width at IAx, 

 1.6 to 1 ; height to width of crown, 5 to 1 ; spread of calyx from base, 1 to 2.3. 

 Surface smooth. Base flush with column facet. Dimensions of type and only 

 known specimen; height of crown to infolding arms, 35 mm.; width at IAx, 7; 

 width at base, 3 ; height of calyx to top of iBr, 1 1 mm. 



