392 PROCEEDINGS OF THE GEOLOGICAL SOCIETY, [Mar, 9, 
ginal plates and appendages thereof, the figure and arrangement of 
the discal plates, and the form and development of the rays :— 
1. Astrogonium. Marginal plates large and smooth towards the 
centre, their inner border encircled by granules. 
2. Gonodiscus, Marginal plates having the entire upper surface 
covered with close-set granulations. 
3. Stellaster. Marginal plates granulated, the ventral segment 
supporting a pendent spine, the rays elongated and tapering to a 
lanceolate extremity. 
Many of these characters are absent in fossil Goniasteride, and 
are therefore valueless for paleeontological purposes ; for this reason 
I have retained the genus Gonzaster for the large pentagonal short- 
rayed forms, and that of Stellaster for those with a smaller disk and 
more elongated rays. 
This division must be considered merely provisional until we 
become better acquainted with the comparative anatomy of extinct 
forms. The very fine fossil discovered by my friend Samuel Sharp, 
Ksq., F.G.S8., in the Ironstone beds of the Inferior Oolite near North- 
ampton, and which forms the subject of this communication, belongs 
to the group Stellaster, in consequence of the smallness of the disk, 
and the length and development of the rays. The absence of pen- 
dent spines or any indication of their presence, warns us, however, 
to be cautious in drawing hasty conclusions as to the true generic 
position of this Starfish, seeing that the presence of this spine is con- 
sidered to be diagnostic of living Stellasters. Whether this fossil 
ever possessed such a spine or not, the mould does not enable me to 
make any positive statement anent. 
STELLASTER SHARPII, Wright. 
Diagnosis.—Body pentagonal, sides arched, rays much elongated 
and tapering to a narrow extremity ; marginal plates thick, surface 
of the same finely granulated. Under surface of the disk covered with 
small close-set polygonal ossicles, having had apparently a very 
granular surface. The circumference of cach ray surrounded by 
sixty pairs of marginal plates, which extend from the centre of the 
arch of one interradial space to the same point of the adjoining area. 
Ambulacral furrows wide, oral opening large. 
Dimensions.—Diameter of the disk two inches from the centre of 
one areal arch to the same point on the opposite one; from ray- 
point to ray-point six inches, depth of the border at the centre of 
the arch three tenths of an inch. . 
Description.--This remarkable fossil is entirely a mould in Iron- 
stone, none of the ossicles having been preserved; but the sharp 
impressions of their forms and sculpture impressed on the Ironstone 
reveal a tolerably correct idea of the anatomy of the plates. 
The Starfish rests upon its upper surface, which is firmly im- 
bedded in the matrix, so that the size, shape, and character of the 
dorsal ossicles still remain to be discovered. Those on the under- 
side of the disk are nearly uniform in size, and are small, pentagonal 
and hexagonal. 
The granulations on the surface of these small bones appear to 
