354 SMITHSONIAN INSTITUTION 



lifted out of the ray, or reduced to a small quadrangular plate obliquely to the left of the 

 radial. i ■ ■ 



The definition as quoted above clearly refers to the latter, and was evidently taken from 

 G. expansus, in which the structure is very plainly shown by Angelin's figure. The list of 

 species, however, included a considerable number of species having form No. i, and some 

 in which the irregularity was not in the possession of a radianal, but in the asymmetric posi- 

 tion of the first plate of the tube, which we know now to be characteristic of all the Taxo- 

 crinidae. No type species was indicated by the authors, but Bather in 1899 (Rep. Brit. 

 Association, p. 923) supplied this defect by proposing G. expansus, which thus becomes the 

 type by subsequent designation. It happens that this is the only one of the species listed 

 which has the character described, and the curious result follows that out of the twelve species 

 originally referred to the genus, only a single one remains under it now. But subsequent 

 discoveries in the American Silurian have added new species, which confirm the validity of 

 the genus and greatly extend its geographic range. Those species having structure No. 1, 

 as already seen, have been transferred to Protaxocrinus. G. excavatus goes very readily 

 under Dactylocrinus; G. loveni to the new genus Meristocrinus; and G. oblongatus, with its 

 synonym G. rigens to Eutaxocrinus. G. (Taxocrinus) punctatus is insufficiently defined, and 

 the original cannot be found ; it is probably a Cyathocrinoid. 



While the excavate posterior basal followed by an anal tube suturally free at one side 

 fixes the generic position of this form without doubt among the Taxocrinidae, it is not easy 

 to draw a satisfactory line between it and the Lecanocrinoid genus Asaphocrinus, because 

 of intermediate stages exhibited by that genus, and by abnormal specimens of G. expansus 

 tending to vary in that direction. The species of the two genera must be considered as in the 

 borderland between their families. Gnorimocrinus is exclusively a Silurian genus ; the three 

 following species are recognized : 



The Species of Gnorimocrinus 

 I. Arms short, heavy throughout, rounded, tapering little. 



Br with lateral angles or buttresses. 



Specimens small. IIBr 3 (or 2) G. expansus. 



Br with lateral margins smooth. 



Specimens larger. IIBr 3 (exceptionally 2) G. cirrifer. 



II. Arms tapering rapidly to the branches. 



RR large and more prominent than succeeding IBr. IIBr 2 or 3 G. varians. 



Gnorimocrinus expansus (Angelin) 

 Plate XLV1I, figs. 1-6 



Taxocrinus expansus Angelin, Icon. Crin. Sueciae, 1878, p. 9, pi. 20, figs. 15, 16. 



Taxocrinus (Gnorimocrinus) expansus, Wachsmuth and Springer, Revision Palaeocrinoidea, pt. 1, 1879, 



p. 50. 

 Gnorimocrinus expansus, Bather, Rep. British Assoc, for 1898 [1899], p. 923; Treatise on Zoology 



(Lankester), pt. 3, 1900, p. 189. — Springer, Jour. Geology, XIV, 1906, p. 515. 



Type of the genus. 



A small species. Crown short, broad, rotund, infolding" about the third 

 bifurcation, widest about IIBr 2 or 3. Height to width at that level, 1 to 1; 

 of calyx to top of axillary IBr, 1 to 1.4; expanding rapidly from BB with spread 

 from base 1 to 5. IBr almost filling the distal face of RR and succeeding them 

 without any conspicuous difference in width. Anal tube very large, resembling 



