35- SMITHSONIAN INSTITUTION 



Protaxocrinus salteri (Angelin) 



Plate XLVI, figs. 1-7 



Taxocrinus salteri Angelin, Icon. Crin. Sueciae, 1878, p. 9, pi. 23, figs. 1, la. 



Taxocrinus (Gnorimocrinus) salteri, Wachsmuth and Springer, Revision Palaeocrinoidea, pt. I, 1879, 



P- Si. 

 Protaxocrinus salteri, Springer, Jour. Geology, XIV, 1906, p. 515. 

 Taxocrinus distensus Angelin, Icon. Crin. Sueciae, 1878, p. 9, pi. 26, figs. 7, ya. 

 Taxocrinus tubuliferus Angelin, ibid., p. 9, pi. 20, figs. II, 12. 

 Taxocrinus austini Angelin, ibid., p. 9, pi. 19, figs. II, no. 



A medium sized species. Crown elongate, widest about IIIBr 5 , where 



height to width is 1.8 to 1 ; calyx at top of IAx, i to 1.3; spread of calyx from 



base to same level, 1 to 2.5. Lateral margins of brachials slightly angular, or 



smooth. Arms broadly rounded, tapering but little to the fourth bifurcation; 



ornamented with small nodes or pustules. Small iBr, followed by perisome in 



first and second axil. Anal tube small. IIBr 3, exceptionally 4. Column as 



large as the base, tapering but little downward. Height of large specimen, 



41 mm. ; width, 23 mm. ; base at column facet, 6 mm. 



This species is similar in general form to P. interbrachiatus, but is more slender below, 

 and differs in the pustulate ornament on the arms, fewer IIBr and smaller anal tube. In 

 addition to Angelin's type I have figured another similar but somewhat larger specimen 

 showing the anal side, with various details from both showing ornament and interbrachial 

 structures. Both these are from Faro. I have also placed under this species several speci- 

 mens from other Gotland localities which are not so characteristic. Among these are: 



(1) The type of Angelin's Taxocrinus distensus (PI. XLVI, figs. 3a, b) ; it has but two 

 plates below the axillary in the right posterior ray, as in the others, and would thus seem to 

 be without a radianal. But the small size of the first plate shows that it is the radianal, and 

 that the specimen is abnormal in lacking the super-radial or IBr^ a defect which is compen-., 

 sated by the addition of an extra IIBr. Allowing for this it agrees well with the type. 



(2) The type of Taxocrinus tubuliferus (PI. XLVI, figs. 50, b), a very young specimen. 



(3) The type of Taxocrinus austini (PL XLVI, figs. 6a-d), another very young, imperfect 

 and distorted specimen, wholly destitute of any diagnostic characters for specific description. 



(4) A fine specimen from Follingbo (PI. XLVI, fig. 4) abnormal in having but one IBr in 

 the left posterior ray, which is compensated by extra IIBr following it. All these agree well 

 enough with the species in the absence of marked angularity on the margins of the rays, and 

 the presence of 3 IIBr in a decided preponderance of the rami. The remaining specimen 

 (PL XLVI, fig. 7), with 4 IIBr in all three of the visible rami, must be considered a strong 

 variant of the species. 



It is difficult to state diagnostic characters which will consistently differentiate this and 

 the two preceding species, and it is possible that all three should be placed together as a 

 variable species with 3 and 4 IIBr under the name P. ovalis. 



Types. Riks Museum, Stockholm, Sweden. 



Horizon and locality. Silurian, Wenlock Group, horizons d and f; Faro, Follingbo, 

 Wisby, Djeywick and Endre, all in the Island of Gotland. 



