TAXOCRINIDAE 379 



from later investigations modified this opinion, and in the Revision of the Palaeocrinoidea, 

 part i (1879), we pointed out the fundamental characters in the structure of the anal inter- 

 radius on which the genus is separated from all those with which it has been confused, save 

 only Onychocrinus, and in which it becomes the representative of a well-defined and larger 

 family group. This conclusion regarding the genus has been accepted by subsequent authors 

 without dissent. 1 



No notice was taken of any anal structures in any of the earlier diagnoses or descriptions 

 of this genus, nor, as was the case in many other genera, of the fact that itl has a dicyclic 

 base. Johannes Muller in 1858 (Monatsber. Berlin Akad., p. 185), was the first to demon- 

 strate the presence of three small plates below those which were before supposed to be the 

 lowest plates of the calyx; and Schultze in 1867 (Echinodermen Eifler Kalkes, p. 32) called 

 these small plates " cryptobasalia " because they are usually hidden by the column. 



The Austins and M'Coy added to Phillips's original list several new species from the 

 English and Irish Carboniferous ; Roemer, Muller, and Schultze four or five more from the 

 Devonian of the Rhineland ; while still others were added by the American paleontologists 

 from the Devonian and Carboniferous of this country. In the meantime Angelin, in 1878, 

 described under this genus several more new species from the Silurian of Gotland ; and two 

 species described by Billings as Lecanocrimis, from the Ordovician of Canada, were referred 

 to it by Wachsmuth and Springer. Thus by the year 1900 the apparent range of the genus 

 had been extended so as to include forms from the Lower Ordovician (Trenton); to the 

 highest Lower Carboniferous (Kaskaskia) ; and more than fifty species had been referred 

 to it. 



Angelin's Taxocrini were separated by Wachsmuth and Springer in 1879 under their 

 new genus Gnorimocrinus, upon rather unsatisfactory characters as then stated ; the genus 

 is now better defined and may be retained as valid, but not all of Angelin's species fall under 

 it. There still remained a great aggregation of species which was not only unwieldy in itself 

 by reason of its number, but objectionable because upon geological grounds it seemed highly 

 desirable to find some basis for separating the Ordovician species from those of the Car- 

 boniferous. Considering the progressive modifications of structure that were known to 

 have taken place among the Inadunata, and the fact that closely parallel changes had occurred 

 in the Ichthyocrinidae, it seemed to the last degree improbable that such a form as Taxo- 

 crinns should persist from the Ordovician to the latest Lower Carboniferous without any 

 modification of more than specific importance. Satisfactory grounds for separation were 

 finally found by me in the anal and brachial structures, forming the basis of several homo- 

 geneous and practicable generic groups. 



T. tuberculatus, one of the species originally included by Phillips, was removed to 

 become the type of Temnocrinus, and falls into a different family. The Ordovician and all 

 but one of the remaining Silurian species were separated under Protaxocrinus and Meristo- 

 crinus. All of these older forms are clearly marked off by the presence of a radianal in some 

 distinctive lower position. 



The subdivision of the Devonian and Carboniferous Taxocrini, in which the radianal 

 has been shifted upward or eliminated, does not follow sharp stratigraphic lines, being based 

 upon a modification in brachials which began in the Devonian and was not concluded until 

 the early Carboniferous. The type represented by the parent genus culminated in the 

 latter part of the Lower Carboniferous, where it was widely distributed and characterized by 



1 The diagnosis of Taxocrinus quoted in Revision of the Palaeocrinoidea, pt. I, p. 43, as being from 

 Phillips, must be taken as Wachsmuth's interpretation of the several definitions, chiefly those of M'Coy 

 in 1844 and 1854, which by some lapsus pennae was placed within quotation marks. It is couched in 

 modern terminology, not employed at those dates. It is also incorrect in stating that the " arms divide 

 upon the third radial," — as Phillips in his definition of Isocrlnus expressly included species with more 

 than " three costals," and the type species, T. macro dactylus, was said to have, and actually has, four. 



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