J. W. Gregory—A new Protaster from Austraha. 25 
the arms; they are about three times as long as broad and some- 
what spindle-shaped, being more bulging in the middle than in F. 
leptosoma, which is the nearest ally of this species; the margins are 
entire and not notched as in that species. The adambulacral elements 
in the “oral pentagons” probably represent the jaw and jaw-plate ; 
the former is long and narrow, abont four times as long as broad, 
and slightly curved at the inner end (Fig. 3, b); the jaw-plate, 
which unites the jaw to that of the adjoining radius, is short and 
thick ; its inner surface is concave, as the two free corners extend 
somewhat towards the centre of the disk (Fig. 4, c). Neither buccal 
nor dental papille nor teeth are shown. 
Each arm consists of a series of pairs of ambulacral ossicles 
(Fig. 2, ao) and adambulacral plates (Fig. 2,1) on each side of a 
median ridge, seen on the abactinal surface (Fig. 2, d): the first 
apparently represent the unfused halves of the ambulacral or verte- 
bral ossicles of Ophiuroids; the second, the lateral or adambulacral 
shields: the nature of the median ridge is doubtful; it may possibly 
represent upgrowths from the ambulacral ossicles comparable to 
those in Brisinga, or it may have some connection with the dorsal 
shields, which are not otherwise indicated. Seen from the abactinal 
aspect, the ambulacral ossicles appear thick and bluntly oval, with 
the longer axis in the direction of the arm, and placed alternately im 
the concavities of the sinuous median ridge; they are distinctly 
Dima stone: — Diameter ofidisk eeMameee) ls... 0...) Heeninerenel idee tl ascralin nde cons 
Diameter to the extremities of the oral pentagons ... 7 mm. 
Width oftarmi ae emibees co, | os spnseay MRee ee Cuerpo une, 
Length of ambulacral ossicles ... ... ... «. s 1mm. 
EXPLANATION OF THE FIGURES. 
Fig. 1, Specimen of Protaster brisingoides, abactinal aspect; nat. size.’ Fig. 2. 
Part of an arm from the same specimen, that which is uppermost in Fig. 1; 
d. median ridge; ao ambulacral ossicle, 7. adambulacral plate: x4 diam. 
Fig. 8. The oral apparatus from another specimen in which the disk is not 
shown; 4. jaw, c. mouth-frame; x4 diam, Fig. 4. A jaw-plate and distal . 
ends of a pair of jaws; x8 diam. 
1 The faint indication of a disk is not shown in the figure, but can be detected in 
one or two of the interradil. 
