702 Proceedings of the Royal Society 
4. Luidia sarsii, Diiben and Kore’n. 
Station 3. Aug. 3 and 4, 1880. Lat. 59° 12' N., long. 5° 57' 
W. Depth, 53 fathoms. Seven examples. 
5. Porania pulvillus (0. F. Muller), Norman. 
Station 3. Aug. 3 and 4, 1880. Lat. 59° 12' N., long. 5° 57', 
W. Depth, 53 fathoms. A single example. 
6. Mimaster tizardi , gen. et sp. nov. 
Station 4. Aug. 10, 1880. Lat. 59° 33' N., long. 7 14' W. 
Depth, 555 fathoms; bottom temperature, 45 0, 4 Fahr.; surface 
temperature, 57° Fahr.; mud. A single example. 
Radii five, marginal contour stellato-pentagonal, interbrachial 
angles sub-acute, the radii tapering gradually to a fine extremity. 
The lesser radius is in the proportion of 45 per cent., R= 120 millim., 
r = 5 4 millim.; breadth of a ray at the base, 58 millim. Dorsal 
profile high and gibbous over the disk. Actinal surface convex. 
Dorsal area covered with a great number of uniform small paxillse, 
closely and equidistantly placed, presenting no definite order of 
arrangement. The paxillse consist of a cylindrical pedicel nearly 
twice as high as broad, surmounted by a crown of 15 to 20 spinelets 
about equal in length to the pedicel, except where they have been 
abraded ; and the spinelets radiate apart very slightly, which gives a 
compact appearance to the paxillse. Papulae in groups of 3 to 5 occur 
between neighbouring paxillse. 
Marginal plates, in ventral and dorsal series, small and sub- 
tubercular in appearance, 37 to 38 in each series between the inter- 
brachial angle and the extremity of the ray. Each’ plate or boss is 
covered with a great number of small spinelets similar to those of the 
paxillse, giving them a round, cushion-like appearance. The infero- 
marginal plates are the largest, transversely sub-oval in form, — the 
length increasing towards the interbrachial angle, and bear not less 
than 100 spinelets. The supero-marginal plates are smaller, usually 
round, and placed rather more aborally than the companion plate of 
the lower series, the pairs standing consequently slightly oblique. 
The ventral plates occupy a great space on the actinal surface, and 
extend up to the very extremity of the ray. Each plate bears a single 
paxilla, which is rather more robust than those on the dorsal surface, 
and carries rather fewer spinelets, which are somewhat longer and 
more widely expanded. In consequence of the size and arrangement 
