NO. 1846. ON CERTAIN ELEUTUBROZOIC PELMATOZOA—KIRK. 53 



antecedent types. As noted above, because of the supposed posses- 

 sion of a persistent proximal columnal the genus has been placed 

 within the Flexibilia. The validity of the grouping upon which the 

 order Flexibilia rests will be discussed more at length during a con- 

 sideration of the affinities of the members of Group II. In this con- 

 nection will be given a more detailed discussion of the homologies of 

 the proximale and its value in classification. As has been described 

 above, there seems every reason to believe that in the case of Milleri- 

 crinus there is no justification of this reference, inasmuch as new col- 

 umnals seem to be formed immediately beneath the basals. The 

 structure of Millericrinus seems to point strongly to a derivation not 

 far out of the line from which the Pentacrinidae were evolved. In any 

 case I can see but slight reason for removing the Apiocrinidse from the 

 Inadunata. One of the main difficulties in the discussion of the 

 genus is the apparently heterogenous character of the forms referred to 

 Millericrinus by de Loriol. It is evident that we have here included 

 highly divergent types, and until these have been resolved into their 

 proper groups by a careful study of the material we can get but an 

 imperfect idea as to the status of the various types. 



Epi-planlcton: Pentacrinus. — Whereas the majority of the crinoids 

 upon temporarily abandoning their sessile habits live as vagile benthos, 

 a few assume the somewhat surprising role of epi-plankton. As has 

 been noted above, Buckland (1837, p. 437), in addition to postulating a 

 detached existence for P^ntocnwws, assumed that in manj^ instances the 

 animals attached themselves to drifting bits of wood and were then 

 carried from place to place. The arguments for such a mode of 

 life can scarcel}'' be better presented than in the words of Buckland 

 himself : 



The specimen of Briarean Pentacrinite at Plate 52, figure 3, from the Lias at Lyme 

 Regis, adheres laterally to a portion of imperfect jet, which forms part of a thin bed of 

 lignite in the Lias marl between Lyme and Char mouth. 



Throughout nearly its whole extent Miss Anning has constantly observed in this 

 lignite the following curious appearances : The lower surface only is covered by a 

 stratum entirely composed of Pentacrinites, and varying from one to three inches in 

 thickness ; they lie nearly in a horizontal position, with the foot stalks uppermost, 

 next to the lignite. The greater number of these Pentacrinites are preserved in such 

 high perfection that they must have been buried in the clay that now invests them 

 before decomposition of their bodies had taken place. It is not uncommon to find 

 large slabs several feet long whose lower surface only presents the arms and fingers of 

 these fossil animals, expanded like plants in a Hortus Siccus, whilst the upper surface 

 exhibits only a congeries of stems in contact with the under surface of the lignite. 

 The greater number of these stems are usually parallel to one another, as if drifted 

 in the same direction by the current in which they last floated. 



The mode in which these animal remains are thus collected, immediately beneath 

 the lignite and never on its upper surface, seems to show that the creatures had 

 attached themselves in large groups (like modern barnacles), to the masses of floating 

 wood, which, together with them, were suddenly buried in the mud, whose accumu- 

 lation gave origin to the marl, wherein this curious compound stratum of animal and 



