424 
Ir, W. K. Fisher on new 
and the arms are the first mar- 
ginal plates (figs. 5 and 6); 
proximal adambulaeral gine 
not higher than long ; gonads 2 
or 4 to each ray. Genotype, — 
Brisinga panamensis, Ludwig . 
. Abactinal skeleton of genital region 
of ray composed of a uniform 
armour of thin, spiniferous, more 
or less overlapping plates, but not 
of independent arches or costie. 
J. Primary plates of disk much 
larger than the others, which 
are small; gonads 2 to each 
ray; an interradial plate, ver- 
tical in position, is interpolated 
between the proximal ends of 
the first adambulacral plates, 
and touches the mouth-plates, 
but does not encroach upon the 
actinal surface as in Colpaster, 
Genotype, Belgicella racovitz- 
ONG, MO GIl oa Se cent 
f?. Primary plates of disk not con- 
spicuous and not distinguish- 
able from the other abactinal 
plates of disk. 
g. An azygous interradial plate, 
shield-shaped and conspic- 
uous superficially on the 
actinal surface, separates the 
first pair of free adambulacral 
plates; gonads unknown. 
Genotype, Colpaster  scuti- 
gerulus, Sladen......... 
. First pair of adambulacral 
plates not separated by an 
azygous plate, but united as 
in Brisinga, and above them 
is a pair of conspicuous, 
united, first marginal plates— 
four in all in each interradial 
angle; gonads numerous, in 
a series along either side of 
theray. Genotype, Freyella 
spinosa, Perrier 
d’. No syzygy, or non-museular sym- 
physis, between the first and second 
adambulacral plates nor between 
the upper part of the second and 
third ambulacral plates, but a nor- 
mal muscular symphysis not diffe- 
rent from the others; no marginal 
plates directly above the first pair 
of adambulacral plates; the latter 
are not united except sometimes by 
the proximal ends; touching the 
Astrolirus, Fisher. 
Belgicella, Ludwig. 
Colpaster, Sladen. 
Freyella, Perrier. 
