72 
TH. MORTENSEN 
(Schwed. Südpolar-Exp. 
To the description of A. cavernosus given by Philipit and, especially, by De 
Loriol (under the name gallegosensis ) the following remarks may be added. 
The hinder part of the labrum does not reach beyond the first ambulacral plate. 
The labrum carries small spines and pedicellariæ. There are generally 5 well devel- 
oped subanal tubefeet, the first of them occurring on the 6th — 7th ambulacral plate. 
The peripetalous fasciole passes over the 15th — 16th plates of the posterior ambu- 
lacra. Genital pores generally 3, sometimes only 2. The test is often unequally 
developed, the right side projecting distinctly beyond the left. The petals are stated 
by De LORIOL to have »une tendance marquée à s’effiler à l’extrémité»; they are 
certainly slightly narrower at the lower end, where they join the fasciole, but they 
are still distinctly petaloid in their whole length, in marked difference from Tripylus 
excavatus. The latero-anal fasciole may be rather distinct in young specimens, and 
also sometimes in larger specimens. 
The spines are rather coarse, as in all the Abatus- species. — The spicules are 
irregular spinous or ramose rods, well developed in the tubefeet of the frontal am- 
bulacrum, very feebly developed in those round the mouth. The sucking disk is 
well developed in the tubefeet of the frontal ambulacrum, the edge of the disk not 
lobate; the rosette plates are broad and well developed, though not reaching the 
edge of the disk. — The sphæridiæ are generally much grooved. 
The pedicellariæ occur in three forms, viz. globiferous, rostrate and tridentate. 
The globiferous pedicellariæ (PI. XIX Figs. 28 — 29, 33), which do not occur on all 
the specimens, are rather large, the valves enclosed by a thick, brown, evidently 
glandular skin. The valves have, as in Schisaster , an interior gland cavity, opening 
at the point of the valve. The opening is surrounded by 2 — 3 teeth on either side, 
sometimes, however, there may be only one tooth on the one side, 2 — 3 on the 
other. The sides of the basal part rather narrow; the blade is rather strongly 
curved. There is no neck; the stalk is simple, without distinct thickening at either 
end. — The rostrate pedicellariæ (PI. XIX Figs. 30, 38, 45) have a rather deep blade 
with more or less serrate edges; the outer end is narrowed. The valves are generally 
not much curved. The neck is well developed, the stalk simple. — The tridentate 
pedicellariæ (PI. XIX Figs. 37, 46, 50 — 51) occur with two or three valves indifferently; 
the larger samples, however, are all three-valved. They reach a size of about 1,3 
mm. length of head. The blade is simply leaf-shaped; in the larger ones there may 
be some meshwork on the outer side of the blade. In the smaller ones the edges 
join in their whole length, in the larger they are apart for some distance below, 
up to half the length of the blade, this part being accordingly narrowed. The edge 
is finely serrate in the outer, joining part, with more or fewer coarser serrations in 
the lower part. The valves of the 2-valved specimens are somewhat compressed, 
otherwise not differing essentially from those of the 3-valved; the apophysis is dis- 
