bo 
Or 
Genera and Species of Brisingide. 4 
lower end of the interradial plate 
is a pair of very inconspicuous plates 
lying in the same plane, and super- 
ficially appearing to be a part of the 
interradial plate *. These are really 
the outer ends of the mouth-plates 
which project dorsally behind the 
first pair of adambulacral plates. 
The latter, by sometimes touching 
at their inner ends, segregate this 
dorsal portion of the mouth-plates 
from the actinal spine-bearing part. 
For this reason they may easily be 
mistaken for two entirely inde- 
pendent plates (see fig. 7). } 
Freyellidea microplax, Lateral view of interbrachium ; the surface of 
the interradial and mouth-plates is dotted. 
e’. Abactinal skeleton of ray com- 
posed of a uniform armour of 
thin, spiniferous, more or less 
overlapping plates as in Freyella, 
not of spaced, independent arches 
or coste; furrow spinelets not 
modified or expanded at the tip. 
Genotype, Freyellidea microplax, 
Bis ere eke ers 6 fe ale gee ees Freyellidea, Fisher. 
e’, Abactinal skeleton of ray con- 
sisting of independent transverse 
arches, composed, on radial area, 
ee cae er ee 
* <The interradial plate described by Ludwig in Belyicella ig perhaps 
the true interradial plate plus these extreme outer ends of the mouth- 
plates, which, unless treated with potash, appear to be a part of the 
interradial plate (Ludwig ‘ Belgica’ Report, 1908, p. 60). 
