MUSEUM OF COMPARATIVE ZOOLOGY. 17 
small colored grains are visible, but these grains are never found except in . 
connection with such deformed tables. In Ankyroderma Marenzelleri, Théel, 
the deposits also seem to undergo similar changes in color. I am much in- 
clined to think that the presence or absence of wine-colored bodies cannot be 
accepted as specific characters. 
Habitat. Lat. 24° 8’ N., Lon. 82° 51’ W. (1877-78); depth 339 fathoms; 
three specimens. 
Trochostoma arcticum, MaRrENZELLER, var. parva, 2. 
This form evidently bears the greatest resemblance to T'rochostoma arcticum, 
but some minor differences exist, in consequence of which I propose to con- 
consider it as a variety. The fifteen tentacles have only a single short branch 
on each side. The body-wall is very thin, but rough from the scattered tables. 
The tail of the animal is destroyed, but the remaining portion of the body 
measures about 60 mm. The color is yellowish gray. The calcareous ring 
possesses five bipartite posterior prolongations. The scattered tables have an 
irregular disk, which is pierced with a varying number of large holes (usually 
few in number) and provided with prolongations or processes running out 
from the circumference of the disk. The disk supports a spire, which is 
irregularly spinous especially towards the free end, and composed of three rods, 
which are transversely united at several points. 
I have examined two other specimens dredged at the same station, the 
largest of which attains a length of only 30 mm. Among the usual tables 
I have found some minute ones resembling those of 7rochostoma antarcticum, 
Théel. This variety probably combines the extremes living in the arctic and 
antarctic seas. 
Habitat. Grenada (1878-79); depth 416 fathoms ; one specimen. 
Trochostoma arcticum, Marenze.ter, var. ccoeruleum, n. 
This variety is distinguished from the northern form only by the abundance 
of pigment in the skin, which gives to the animal a bluish-violet color. Pos- 
sibly also the disks of the tables are larger and more regularly formed. The 
tentacles have only a single pair of short branches near the top. 
Habitat. Grenada (1878-79); depth 553 fathoms; one specimen, about 
80 mm. long. 
Caudina arenata, Govutp, var. armata, n. 
So far as I can observe, the specimens agree in all respects with those 
described by Selenka, Semper, and Marenzeller, except in the shape of the 
deposits. The body itself of the largest specimen measures about 50 mm. in 
length, and the narrow caudal portion is 35 mm. long. The fifteen tentacles 
VOL. XIII. — No. 1. 2 
