56 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.41. 



Apparently the main objection to referring all the " Camarocrinus" 

 to Scyphocrinus lies in the vertical range of the forms. Putting aside 

 the Bohemian beds, the correlation of which, with American forma- 

 tions, can be but approximate at best, we have " Camarocrinus^' 

 ranging from the late Manlius into what is correlated with the lower 

 New Scotland.^ This is certainly not an excessive vertical range for 

 a crinoid genus. On the other hand, the possibility of the acquisi- 

 tion of such a highly specialized organ, which is without a close 

 parallel in all the Pelmatozoa, as a result of parallelism or converg- 

 ence, is beyond the bounds of legitimate speculation. It is probable 

 that during the long period of time in which this highly specialized 

 float was being evolved sufficient changes may have taken place in 

 the crown to warrant generic separations. Among the forms as we 

 know them, however, the float has essentially the same structure, and 

 it seems probable that the animals themselves did not vary greatly. 

 Again, the Bohemian occurrence is considered the lowest, while the 

 Tennessee-Oklahoma occurrence is at the highest known horizon in 

 which " Camarocrinus" occurs. If the crinoids to wliich the floats 

 belong are referable to the same genus, even though found at the 

 extremes of the geological range of "Camarocrinus," there seems no 

 way of escaping the conclusion that the intermediate forms likewise 

 must be considered as belonging to Scyphocrinus. It seems as firmly 

 established, then, as such a thing may well be, that the bodies known 

 as Camarocrinus or Lobolitlius are the distal expansions of Scypho- 

 crinus stems. 



Schu chert (1904) has so thoroughly described the structure of these 

 lobohths that there is little more to be said in that regard. More 

 recently Sardeson (1908) has written in regard to these bodies, par- 

 ticularly as to their evolution. An extended discussion of the subject 

 is somewhat out of place in the present paper and will be reserved 

 until such time as the species of Scyphocrinus in America, of wliich 

 there are no less than four, are described.^ 



1 Fritsch (1907, p. 5) has described and figiired a large roughly lobate object from a quartzite of Etage D 

 as Camarocrinus (Lobolithes) quarzitarum. The nodular mass is some 21 cm. in breadth by 15 cm. in length, 

 and seems to be divided into five irregular lobes. There is apparently no good reason for considering this 

 mass other than in the light of a quartzitic concretion. It certainly bears no relation to " Camarocrinus." 



2 In connection with the remarkable habits of Scyphocrinus should be noted an interesting feature occa- 

 sionally shown by the stalked young ofAntedon bifida (rosacea). Mr. A. H. Clark has called my attention to 

 a passage by W. B. Carpenter (1866, p. 726) in which the young are described as floating at the surface in an 

 inverted position. How this position is maintained Is not stated, but it would appear that the expanded 

 basal disk has much to do with the matter. It even seems possible that cavities within the disk may 

 convert this organ into a sort of float not greatly dissimilar to that oi Scyphocrinus. 



In Antedon the acquisition of such structures may be pathologic, but the case nevertheless suggests many 

 Interesting possibilities. For instance, it may well be that the float of Scyphocrinus had its inception in such 

 an aberrant saltation, being flrst acquired in a rudimentary way by the very young crinoids. Again, it 

 does not seem Impossible that such floating disks may largely have been possessed by various crinoid lines 

 as normal structural features. If this be true it is evident that we have a factor that might be of high 

 importance as affecting the distribution of the Crinoidea. 



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