INSERTAE SEDIS 453 



RHOPALOCRINUS Wachsmuth and Springer 

 Plate LXXV, figs, na-d 



Rhopalocrinus Wachsmuth and Springer, Revision Palaeocrinoidea, pt. I, 1879, P- 57; ibid., .pt. 3, Sec. 2, 

 18S6, p. 176.— Bather, Rep. Brit. Assn. for 1888, 1899, p. 923; Lankester's Treatise on Zool., pt. 3, 

 1900, p. 191.— Springer, Amer. Geol. XXX, 1902, p. 95; Jour. Geol. XIV, 1906, p. 484— Zittel- 

 Eastman, Textb. Pal. 191 3, I, p. 206. 



Genotype. Ta.rocrinus gracilis Schultze (not Taxocrinus gracilis Meek and Worthen), 

 Monogr. Echinod. Eifel Kalkes, 1866, p. tf, pi. 4, figs. 3, 3a. 



Distribution. Middle Devonian, Eifel, Germany. 



In proposing this genus under the family Ichthyocrinidae for the species which Schultze 

 had described under the name Taxocrinus gracilis, Wachsmuth and Springer pointed out its 

 close relationship in arm structure and in the possession of an elongate ventral tube to such 

 genera as Synbathocrinus, and expressed doubt whether it belongs to the Ichthyocrinidae, 

 which family as then conceived embraced all the Flexible crinoids. In the revised edition 

 (191 3) of Zittel-Eastman's Textbook of Palaeontology, page 206, it is stated that this form 

 " might be described as a dicyclic Synbathocrinoid, with some interbrachial plates." This 

 characterization was induced largely by the presence of the strong ventral tube, apparently 

 extending to the full height of the arms. This fact was not shown by Schultze's figures, but 

 I have been enabled by some further preparation of the type specimen, now in the Museum 

 of Comparative Zoology at Harvard, to illustrate the actual structure in this respect very 

 clearly, as shown by figures lib, c on Plate XXV. The interbrachials (fig. lid), the pres- 

 ence of which is contrary to the dominant character of the typical Inadunata, bear consider- 

 able resemblance to those found in some primitive Inadunates like Cupulocrinus, as shown 

 upon the same plate, figures 2a, 5 ', they are irregular and may be only sporadic, as they 

 occur in but a single interradius. 



But for the tube, the affinities of the genus would be decidedly with Cupressocrinus, 

 which it strongly resembles in shape and formation of the arms, especially in the presence 

 of the very short first brachial, which is a marked character in all the species of that genus. 

 The two genera are similar in having a dicyclic base, of which in Rhopalocrinus the lower 

 ring is represented by an undivided disk as in Cupressocrinus. Schultze's figure 3, showing 

 a suture directly below the posterial basal, is incorrect, as is my copy of it at figure 11a, in 

 which the error was inadvertently preserved. In this respect the statement of Wachsmuth 

 and Springer (Revision Palaeocr. pt. 1, p. 58), that this form has " underbasals 3," must 

 also be corrected. Unfortunately but a single specimen of the type species has ever been 

 found, and we do not know to what extent the singularly composite characters which it 

 presents are persistent. 



On account of the massive tube, which as now disclosed by the new figures represents 

 an extension of a tegmen composed of solid plates, this genus must be excluded from the 

 Flexibilia. As to this character it belongs rather to the Fistulate Inadunata. 



