245 
to modification according to tlie development of the anal 
plates. One of the first-radials generally rests upon the? 
upper truncate margin of a sub-radial. 
Free radials variable in number and also in relative 
breadth, according to the species; generally broader than 
long. 
Arms bifurcating more or less frequently ; ossicula) 
arranged in single series, with their articulating margins 
parallel. "Brachial plume'' meagre, and generally incapable 
of being so closely apposed as was the habit in such genera 
as Zeacrinus and Scaphiocrinus. 
As thus limited, the genus Poteriocrinus will include the 
following British Carboniferous forms, viz. : — 
(i.) P. crassuSy Miller. 
P. spissus, De Koninck. 
P. conicus, Phillips, 
(ii.) P. jjlicahcs, Austin. 
P. impressuSy Phillips, 
(iii.) P. radiatus, Austin. 
P. quinquangularis (Miller), Austin. 
III. — Diagnoses and Descriptions of Allied Genera, with 
Synonymij of the Species assigned to each. 
Dactylocrinus, gen. nov. 
Calyx, very elongate ; contour, truncate conoid. 
Basal plates, five, long ; of the same character as in Poterio- 
crinus (ante). 
Siib-radials, five, large ; longer than broad. 
First radials, connected laterally ; pentagonal, rather long. 
Free radials, a single plate to each ray (with an additional 
intermediate plate in some species) ; very elongate (the length 
generally exceeding the width several times) ; the upper 
margin bearing two articular facets. 
