OF THE SIBOGA-EXPEDITION. 145 
almost completely close what would otherwise be a large 
rhombic water-pore; the second brachial is much larger 
than the first, and is in direct dorsal view almost an 
equilateral triangle; the outer border is slightly concave 
and the distal edge is very finely spinous; the third and 
fourth brachials (together forming the first syzygial pair) 
are slightly longer interiorly than exteriorly, about twice 
as broad as long in the median line; the sides are slightly 
concave and the distal edge is very finely spinous; the 
following brachials rapidly become oblique, and after the 
second syzygy triangular and as long as broad, with very 
finely spinous edges, further out on the arm obliquely 
wedge-shaped; the brachials have projecting and over- 
lapping finely spinous distal edges, and their dorsal surface 
is marked with fine parallel longitudinal ridges. 
P, is 12 mm. or 13 mm. long and is composed of 
twenty segments of which the first is slightly longer than 
broad, the second about half again as long as broad, the 
third about twice as long as the proximal length, and the 
fourth and following about two and one half times as 
long as broad; this is the longest pinnule on the arm and 
is smooth, rather stiff, moderately stout, composed of com- 
paratively long segments, recalling in its general structure 
P, in the larger species of Psathyrometra; it tapers 
moderately in its proximal third but more gradually from 
that point onward; the segments are closely joined, their 
lines of union being fine and straight as in the stiffened 
pinnules of the species of Stephanometra; P, is 10 mm. 
to 10.5 mm. long with seventeen segments, similar to P, 
but tapering a trifle more evenly; P, is 8 mm. long 
with thirteen or fourteen segments, similar to P, and 
P, but proportionately smaller and with slightly more 
elongated segments distally; P, is 5.5 mm. long with 
twelve or thirteen segments, similar to P, but propor- 
tionately smaller, with slightly longer distal segments; P, 
is 5.5 mm. long with twelve or thirteen segments resem- 
bling the preceding but more slender and with longer 
Notes from the Leyden Museum, Vol. XXXIV. 
10 
