IO 
TH. MORTENSEN, 
(Schwed. Südpolar-Exp. 
If it is correct, what seems to be indicated by the retension of the central pore, 
that the stalk is retained for a considerably longer period than in other Crinoids, this 
will point towards the fossil Thiolliericrinus ; in this form also the basalia are similar 
to those of Notocrinus , and likewise the centrodorsal is somewhat similar. 
The diagnosis of the new family must be as follows: 
Fam. Notocrinidae n. fam. 
Cirri robust, short jointed; cirrus sockets in io vertical columns. Centrodorsal 
with deep radial pits and large basal groove. Basalia present. Perisomatic plates 
well developed, thick; the anal plate is retained. Pinnules robust, with short, cylin- 
drical joints. Genital organs situated in the arms, not in the free part of the pinnules. 
Only genus known: Notocrinus MRTSN. 
Ten arms. Cirri XXX — XL, with 40 — 60 joints. Brachials quite smooth. Pi 
and P 2 about equally long, with 15 short joints. Side and cover plates strongly de- 
veloped on the ambulacra. Viviparous. 
Fam. Antedonidæ A. H. CLARK. 
2. Isometra vivipara MRTSN. 
PL I, Figs. 6 — 10; PI. II, Figs. 5 — 7. 
Antedon hirsuta P. H. Carp. K. A. Andersson : Brutpflege bei Antedon hirsuta Carpenter. 
Wissensch. Ergebnisse d. Schwed. Südpolar-Exp. 1901 — 1903. Bd. V. 
1904, p. i — 7. Taf. I— II. 
Isometra sp. A. H. Clark: Die Crinoiden der Antarktis. Deutsche Südpolar-Exp. XVI. 
Zoologie Bd. VIII. 1915, p. 106, 146. 
Isometra vivipara. Th. Mortensen: Notocrinus virilis n. g., n. sp., a new viviparous Crinoid 
from the Antarctic Sea. Preliminary Notice. Vid. Medd. Dansk Naturh. 
Foren. Bd. 68. 1917, p. 208. 
Centrodorsal low, wider than long, rounded-conical; the dorsal pole smooth, 
rounded, without cirrus sockets; the ventral edge somewhat irregularly sinuate, with 
prominent interradial corners. Cirrus sockets rather closeset, irregularly arranged or, 
partly, forming irregular rows (Fig. 6). 
Cirri ca. XXV — XXX, 28 — 35 (Fig. 7). The joints are short, those from ca. the 
4th to the 10th somewhat longer than the rest. Beyond the middle of the cirrus 
there is a fairly prominent, rounded, dorsal »spine«; on the distal joints it is nearly 
obsolete. Opposing spine erect; terminal claw short. The upper, longer cirri are 
turned upwards, protruding over the disk between the arms (PI. I, Fig. 10). 
Radiais low, the corners not produced. Costals nearly rectangular, more than 
