KEPOET ON THE MYZOSTOMIDA. 
35 
brownish -yellow colour. Not only is the marginal area of these specimens more trans- 
parent, but also the skin of the back, from absence of pigment, and the base of the hook- 
apparatus is plainly visible through it. This specimen, which is 2 '5 mm. long, has an 
oblong cavity in the middle of the back, from wdiick radiate a number of line furrows, 
separating the parapodial sectors from each other. The dorsal tubercles are visible, but 
much smaller than in the larger individuals. In another specimen also from Anteclon 
eschrichti (Station 48), 1'6 mm. long, the dorsal tubercles were scarcely visible, even with 
a lens. 
Hosts. — (a) Antedon eschrichti, Mull., sp., from north Greenland (Proven), found in 
50 fathoms, by the late Director Olrik, Copen- 
hagen Museum. 
,, ,, from Jan-Meyen, by Norwegian Arctic Expedition, 
Bergen Museum. 
„ „ “ Porcupine,” 1869, 60° 14' N., 6° 17' W., 632 
fathoms. The specimen could not with certainty 
be set down as Myzostoma gigcis. 
,, ,, from 76° 51' N., 44° 20' E., 145 fathoms ; Station 21 
(September 7th) of the Dutch Arctic Expedition. 
,, ,, or Antedon qucidrata, P. H. C. Station 48 (Le 
Have Bank) of the Challenger Expedition. 
,, ,, from 74° 71 ' 4" N., 50° 23' E., 84 fathoms; Station 
21 (July 7th) of the Dutch Arctic Expedition. 
(b) Antedon carinata, Leach, sp., Bahia, Challenger Expedition. 
12. Myzostoma testudo, n. sp. (PI. I. figs. 18-24). 
I examined two specimens of this species ; one measured 4 mm. in length, the other 
2‘5 mm. 
, The larger individual has much the appearance of an oval thickish plate, the margin 
of which is bent ventrally in such a manner that the animal appears of a convex lenticular 
shape from above, and concave from below. Its colour is a light sepia brown ; the back 
is sculptured in two different ways, being covered by a number of small tubercles, and 
also divided by furrows into larger areas, so that it has much the appearance of tortoise- 
shell. Two longitudinal furrows enclose a central area (figs. 18, 19), which gradually dies 
away, but again increases at the hinder margin of the body, the latter portion being sepa- 
rated off from the rest by a furrow ; this middle area has the appearance of a goblet with 
a broad base. There are also on either side five oval elevations arranged in a semi- 
circle ; these look at first sight as if they were ten small individuals, but a closer examina- 
tion shows that they are merely elevations, covering the basal ends of the hook-apparatus 
(cf. Genus Myzostoma, pi. viii. fig. 2). There are twenty cirri present, each of which is 
