247 
Miller, in 1821 (I.e.), when describing P. tenuis, himself 
expressed doubt as to the correctness of including the crinoid 
which he so named in the same genus as P. crassus, Miller. 
The P. isacohus of MM. Austin seems identical with the 
present species. In any case it is very much nearer than the 
fossil figured by them as P. tenuis ! It should not be lost 
sight of, however, that in these forms the differences of 
appearance between various stages of growth may, in all 
probability, have been very considerable. 
Dactylocrinus elongatus, miJiL 
Poteriocrinus rostratus, Austin, pars. Monog. Rec. and 
Foss. Crinoidea, pi. 9, fig. 2b. (caet. fig. exclu.) 
One of the fossils figured by MM. Austin under the 
name of P. rostratus, differs so widely from the others 
included by these authors under the same denomination, 
that little or no hesitation can be felt as to the correctness 
of its removal from that species. 
MM. Austin themselves remarked (I. c. p. 8-1,) on the 
affinities existing between P. rostratus and P. tenuis. 
SCAPHIOCRINUS. Hall. 
Calyx, broad, depressed ; contour turbinate or basin- 
shaped, gradually enlarging to the base of the arms. 
Basal plates, five, small. 
Siih-radials, five, small ; hexagonal, except that on the 
anal side, which is truncated above by the first anal plate. 
First radials, broad, pentagonal, with the ui)per side 
straight or slightly concave. 
Free radials, a single scries only, pentagonal, with the 
lower side straight ; often much elongated, and the plate 
contracted or concave on each side. 
Arms, double from their origin ; and continuing simple 
to the extremity, or once bifurcating at a considerable 
distance from the primary arbicuhir radial ; ossiculac (arranged 
