220 PROOEEDINQS OP THE ACADEMY OP [1886. 



being here absent, and the space which they should fill left vacant 

 in the fossil. In all these species the top stem joint occupies the 

 same position toward the basals that it does in the two 

 species in which the underbasals are in place, although the 

 plate varies considerably in form. In some of them it ap- 

 pears as if forming a part of the cahx, in others as an ordinary 

 stem joint. In some species it is much wider than the succeeding 

 joints, in others of the same width ; but there are all possible 

 gradations between the extremes. In all of them, however, the 

 plate rests against the outer walls of the basals as in Mill, poly- 

 dactylus, not within the basal ring, and in all of them the basal 

 concavity, whether large or small, is completely filled bj?^ the top 

 stem joint. 



It is very interesting that in the two cases in which De Loriol 

 accidentally discovered underbasals, these were separated from 

 the basals, and are closely attached to the column, which goes to 

 prove that probably already a partial resorption of the plates 

 took place. It suggests further that the union with the under- 

 basals was tighter than with the basals, that probably the former 

 was effected by common suture, the other by S3'Z3^gy or some other 

 loose way, the apposed faces being either striated or showing 

 traces of fossae. 



A near approach to the structure of Millericrinus polydactylus 

 we find in Mill. Piletti (PL 63), in which no underbasals were 

 observed, but the lateral faces of the basals (fig. 8 a) show clearly 

 that underbasals were once present. The column also here, from 

 the first joint down, is strictl}^ interradial, the axial canal small 

 and round, and not in proportion to the large open space between 

 the basals. The basal concavitj^ is funnel-shaped, very deep, 

 wide at the outer end. The upper stem joint is large, and extends 

 in width considerably beyond all succeeding joints. 



A similar base exists in Mill. Milleri (PI. 96), in which again 

 the upper columnar joint is laterally extended and strictly inter- 

 radial, the columnar canal round, and much smaller than the 

 open space within the basal ring, which is star-shaped, the rays 

 directed radiall3^ 



A very different base is figured by De Loriol in Apiocrinus 

 magnificus (Pts. 46-48), in which the top stem joint takes the 

 form of the anchylosed underbasal disk of the Palseocrinoid genus 

 Stemmatocrinus. A comparison, however, with other species 

 proves very clearly, that it is a top stem joint of a very extreme 



