202 SCIENTIFIC RESULTS OF THE 
without armature. The tongue with transverse thickenings of the 
rhachis; the lateral plates somewhat depressed ; the two first different 
from the rest, larger and with a denticle at the root of the hook ; the rest 
without any such, the external quite without a hook. A sucking-crop 
on the upper side of the bulbus pharyngeus, but sessile, depressed con- 
ical, and not consisting of two symmetrical halves. The large 
stomach free on the surface of the liver. The glans of the long 
penis with a strong and quite peculiar armature, consisting of strong 
hooks, partly simple, partly bifurcate and partly digitate, with strong 
digitations. The vagina with a peculiar armature of high palisades. 
This interesting genus externally most resembles the Lamellidorides, 
both in reference to the nature of the back, to the form and size 
of the gill and in the want of armature of the lip-disk; the region of 
the openings of the rhinophor-holes differ in the want of a glabella 
and by the presence of a larger number of surrounding papille. The 
genital opening somewhat recalls the Acanthodorides, as do also the 
(tripinnate) branchial leaves and the sucking-crop, but this is not 
divided in two distinct halves as in this last genus. The armature 
of the tongue is very different from that of the Lamedlidorides, 
Adalariz and Acanthodorides ; the large hook-formed lateral plates 
of these genera are wanting, and in their places are two large de- 
pressed lateral plates, with small hooks; the external plates somewhat 
recalling those of the Adalarix; the rhachis rather. broad, with 
transverse thickenings of the cuticula, corresponding to the rows of 
plates. In the very peculiar form of armature of the glans penis, and 
by the peculiar clothing of the vagina, the Akiodorides differ from all 
the above-cited genera. 
Only a single species of the genus is hitherto known, the new one, 
that will be described below. 
1. Ak. lutescens, Bgh., n. sp. Oceanum Pacificum. 
1. Ak. lutescens, Bgh., n. sp. Pl. IV, fig. 3; pl. V, fig. 11-14; pl. VI, fig. 1-20; 
pl. VII, fig. 1-8; pl. VIII, fig. 1-2. 
Color lutescens. 
Habitat. Oceanum Pacificum septentrion. (Nazan Bay). 
Of this form I have had a large single specimen for examination, 
obtained in August, 1873, by Dall, on stony bottom, at low water, in 
Nazan Bay, Atka Island, Aleutians. 
According to Dall, the color of the living animal was “ yellowish- 
white ;” preserved in spirits, it was of a uniform dirty yellowish color. 
