NO. 1846. O.V CERTAIN ELEUTHEROZOIC PELMATOZOA—KIRK. 39 



The evidence afforded by numerous writers points strongly to the 

 conchision that among these fossil forms a detached mode of life was 

 largely maintained. Indeed in many of these early Pentacrinidae, 

 the degree of specialization exhibited by the organism is even greater 

 than in the case of the recent forms. 



Pentacrinus. — Perhaps the first ascription of a detached existence 

 to a stalked crinoid may be credited to Buckland. In writing of 

 the fossil Pentacrinus he says in part (1837, vol. 1, p, 436) : 



The root of the Briarean Pentacrinite waa probably slight, and capable of being 

 withdrawn from its attachment. The absence of any large solid secretions, like those 

 of the Pear Encrinite, by which this Pentacrinite could have been fixed permanently 

 to the bottom, and the further fact of its being frequently found in contact with 

 masses of drifted wood converted into jet, leads us to infer that the Briarean Penta- 

 crinite was a locomotive animal, having the power of attaching itself temporarily 

 either to extraneous floating bodies, or to rocks at the bottom of the sea, either by its 

 side arms, or by a movable articulated small root. 



Not only did Buckland consider these forms free, but as vnW be 

 shown subsequently, in many cases he supposed an epi-planktonic 

 existence to have been assumed by the crinoids. 



Quenstedt and de Loriol both predicate a free existence for Penta- 

 crinus hriareus ^ and its allies, a conclusion in wliich Carpenter con- 

 curs. According to Quenstedt (1876, p. 271) he beUeved that they 

 "kontenn gleichsam als eine Comatula betrachtet werden, deren Knopf 

 zu grosserer Lange in einer Zeit heranwuchs, wo es noch keine eigent- 

 hchen Comateln gab." de Loriol (1878, p. 12) goes rather more into 

 detail relative to the maintenance of an eleutherozoic habit by these 

 forms. It is to be noted that he offers a rather novel suggestion 

 relative to the method of locomotion in the case of these animals. 

 He believes: "qu'ils avaient, a Tetat adulte, une tige court, fibre, et 

 qu'a I'aide de leurs cirrhes tres nombreux et tres longs ils pouvaient 

 nager facilement et se transporter, rapidement peut-etre, d'un lieu a 

 un autre; ils avaient aussi la faculte de se fixer a quelque objet, 

 lorsqu'ils en avaient le desir, au moyen des crochets dont est munie 

 I'extremite de leurs cirrhes." 



The column of Pentacrinus hriareus as described by de Loriol 

 (1884-1889, p. 385) is short and composed of columnals of uniform 

 size. Each columnal is a nodal and bears a verticil of cirri. These 

 cirri are long and liighly specialized. On the whole this species 

 indicates a degree of specialization in its adaptation to a detached 

 existence scarcely approached by any recent form. A column 

 essentially similar in structure has been described by de Loriol 

 (1878, p. 7) in the case of Pentacrinus dargniesi. The stem in this 

 species is held to be short and is tliickly set with cirri winch range 



1 Bather (1898) gives Pentacrinus hriareus as a synonym otP.fossilis of Blumenbach. I here use P. hriareus 

 as that is the designation employed by the various authors cited. I, however, feel in no wise competent 

 to pass on the validity of the name. 



