TAXOCRINIDAE 



357 



EUTAXOCRINUS Springer 

 Plates XLVII, XLVIII, XLIX, L, LXXV 



Eutaxocrinns Springer, Jour. Geology, XIV, 1906, pp. 403, 519. — Zittel-Eastman, Textbook Paleontology, 

 1913, p. 205. 



Fig. 48. Eutaxocrinus 



Taxocrinidae with rays not abutting over interbrachials. Infrabasals low, 

 taking little part in calyx wall. Posterior basal elongate. Radianal, if present, 

 only in upper oblique position. Interbrachials few or none. Primibrachs two. 

 Arms dichotomous, usually more or less divergent. Column usually enlarging 

 next to calyx. Otherwise as in Taxocrinus. 



Genotype. Taxocrinus affinis Miiller. 



Distribution. Silurian to lower part of Lower Carboniferous; Continental 

 Europe, the United States and Canada. 



This genus was proposed by me to receive those species of Taxocrinus without a 

 radianal in the lower positions and having only two primibrachs. This division has a strati- 

 graphic significance which lends support to its recognition ; for whereas the group of species 

 here assembled begins in the Silurian, culminates in the Middle Devonian and ends at the 

 very base of the Lower Carboniferous, the parent genus as it is left after the removal of 

 these species begins in the Devonian, culminates in the middle of the Lower Carboniferous 

 long after the extinction of Eutaxocrinus, and continues with characteristic species to the 

 end of that epoch. In other words Eutaxocrinus is essentially a Devonian, and Taxocrinus 

 essentially a Carboniferous, genus. The separation has proved to be a useful one from the 

 viewpoint of the systematist, because Taxocrinus, even after the removal of some other 

 genera on account of the radianal, still remained a somewhat unmanageable genus. The 

 characterization of the species is on the whole satisfactory, and with the exception of one or 

 two which are imperfectly known they are recognized without difficulty. 



The Silurian species, E. oblongatus, is somewhat aberrant in its arm structure, having 

 transitional features which make its position here not free from doubt. Leaving this out of 



