THE ECHINODEKMS OF THE WOODS HOLE TtEGION. 569 
Remarks. — This is another of those holothurians of which we know altogether too little. It was 
first dredged on Georges Banks in 1872, and Yerrill afterwards found it in the Bay of Fundy. Theel 
(1886) reports specimens from off the coast of Delaware; they were remarkably large, and he says 
“the anus possesses five calcareous teeth.” Yerrill does not mention “anal teeth ” nor calcareous ring. 
The latter, Theel says, resembles that of Thyone fusus. I have never seen a living specimen of this 
species, but in the fall of 1899, Dr. II. C. Bumpus sent me some alcoholic specimens which I under- 
stood were dredged in Narragansett Bay, and I have also had 5 specimens dredged by the Fish Hawk in 
Vineyard Sound in 1901. None of these specimens were much over 40 mm. in length. They answer 
well to Verrill’s description, except that the disks of the tables rarely contain 20 holes, while he says 
20-24. Theel says that in his specimens the holes were sometimes as many as 20. As for the “anal 
teeth” which he mentions, they may have been due to the age of his specimen, which was twice the 
size of any of mine. It is by no means certain that sea, bra is really distinct from the European fusus, 
but the matter cannot be decided without more material. Naturally we know nothing of its habits 
or development. 
5. Thyone unisemita (Stimpson). (PI. 11, figs. 68, 69; pi. 12, figs. 86-90.) 
Gucumaria fusifnrmis Desor, 1848 ( non Forbes). 
Anaperus unisemita Stimpson, 1851. 
Stereoderma unisemita Ayres, 1851; Verrill, 1873b; ThCel, 1886. 
Thyone unisemita Ludwig, 1892. 
Description. — Length 75 mm. (Verrill) or less; diameter, when normally extended, about one- 
third of the length or less. Body tapering to both ends, which are more or less curved upward. 
Cloacal opening, terminal, not provided with “teeth,” and with no specially prominent papilla; about 
it. Tentacles 10, 2 ventral smaller than the others, which are rather long and slender, stalked, and 
not profusely branched at tip. Pedicels short, quite uniformly distributed over the dorsal surface and 
on the sides; ventrally there is a distinct double row in the midventral radius, and on each side a 
narrow strip of skin, wholly free from pedicels; it is from this peculiar arrangement that the species 
has received its name. Calcareous deposits, perforated plates (fig. 89), mostly regular, and with 4 
holes, but often larger, irregular, and with more holes; plates usually smooth, frequently with knobs 
in the pedicels, which lack terminal plates; supporting rods (fig. 90) rather few, broad, flat, with 
narrow holes, sometimes with knobs, and occasionally projecting spines; in the tentacles, supporting 
rods (fig. 88) large, perforated, and rather numerous; near the tips of the branches they are much 
curved. Calcareous ring (fig. 86) well developed, wide, radial and interradial pieces of nearly equal 
size, but the former with a wider notch in the posterior margin, though there are no posterior prolon- 
gations. Stone canal single, with a small and poorly developed madrepore plate (fig. 87). Polian 
vessel single. Color in life white or yellowish-white, tentacles orange-yellow. 
Range. — Grand Bank, Newfoundland, to Narragansett Bay; 17 to 22 fathoms, probably more. 
Remarks. — Another uncommon holothurian, of which we collected half a dozen specimens in 
August, 1902, at Crab Ledge, on sandy and gravelly bottom. All of these were small, from 8 to 25 
mm. in length, but several had the ovaries full of apparently mature eggs. Stimpson ’s specimens from 
Grand Bank and Massachusetts Bay were about 2 inches in length, while a specimen dredged by 
Packard, south of Marthas Vineyard, was about 3 inches long. Specimens kept alive at the labora- 
tory were very sluggish, and extended the tentacles very little; the color of the latter is in striking 
contrast to that of the body. Besides the localities already mentioned, this species lias been taken on 
Nantucket Shoals, off Gay Head, and in Narragansett Bay. 
6. Caudina arenata (Gould). (Plate 11, fig. 73; plate 13, figs. 103, 104.) 
Chirodota arenata Gould, 1841. 
Caudina arenata Stimpson, 1853. 
Description. — Length 100 to 175 mm., with a diameter about one-eighth as great; the posterior 
third of the animal constitutes what we may call the caudal portion, and this has a diameter of only 
a few millimeters. Integument translucent and smooth, or finely granular. Cloacal opening terminal, 
surrounded by 5 very small papilla;. Tentacles 15, equal, each with four short, finger-like digits. Cal- 
careous deposits (fig. 104) in the form of tables, with smooth, flat, nearly circular or oval disks, each 
with a large central hole, and a more or less regular peripheral series of 8 to 12 holes; the central 
hole appears from above like 4, as the 4 legs of the spire cross it; there are often a few small holes 
