252 
Scaphiocrinus resembles the genus Zeacrinus in the 
depressed basin-shaped form of the calyx, though in the 
latter type the base is sunk in a deep concavity which usually 
hides the basal plates entirely from view. The two genera 
are further distinguished by the characters of their brachial 
plume ; in Zeacrinus, the free radials are broad and touch 
one another lateral^, having the arms many branched, and 
composed of broad, short ossiculae with parallel margins; 
whilst in Scaphiocrinus, the free radials are usually more 
elongated, with generally more or less intermediary space 
between ; and the arms are seldom, if ever, bifurcated more 
than once ; and are composed of wedge-shaped plates, having 
one side longer than the other. 
Although Dacttjlocrinus resembles Scaphiocrinus, in posses- 
sing but a single series of free radial plates in each ray, it is 
readily distinguishable from that geiius by the obconical and 
elongate form of calyx, which in Scaphiocrinus is depressed 
and turbinate ; and yet further separated by the relative pro- 
portion of the plates, all of which in Dactylocrinus greatly 
exceed the breadth by the length. The arms, too, present a 
very marked feature of difference, being in Dactylocrinus of 
meagre habit and composed of very elongate ossiculce, with 
generally parallel articular margins, and are quite incajDable of 
being folded together, or brought into close lateral contact ; 
whilst in Scaphiocrinus, the arm-plates are cuneiform, and 
generally form, when closed, a compact and somewhat elongate 
brachial plume. 
Explanation of Plate. 
The Eeferences indicate the Original Figures. 
Fig. 1. — Poteriocrimis, Miller. 
{Cf. Austin, Monog. r. & f. Crinoidea, pi. 10, 
fig. 1, restored.) 
