STELLASTER. 



165 



Ironstone beds of the Inferior Oolite near Northampton, appears to belong to 

 the group Stellasfer, in consequence of the smallness of the disk and the length 

 and development of the rays. The absence of pendant 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 kind of 

 spine is considered 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 about. 



Stellaster Shaepii, Wright, n. sp. PI. XX. 



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 each 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 channels narrow, 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. 



JDescription. — This remarkable fossil is entirely a mould in Ironstone, 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 imbedded 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, penta- 

 gonal, and hexagonal. The granulations on the surface of these small bones appear to 

 have been very large, whilst those on the marginal tesserse were very small. 



Affinities and Differences. — This species resembles Stellaster Berthandi, from the 

 ' Calcaire a Entroques,' Macon ; it differs, however, from that form in being larger, and in 

 having the interradial spaces more arched and the rays themselves much larger. But the 

 marginal tessera and discal ossicles are very much alike. 



The mould, however, does not give the character of the granulations. It differs from 

 Goniaster olitusus, Wr., from the Inferior Oolite of Crickley, in having longer and more 

 lanceolate rays, and from Goniaster Hamptonensis, Wr., from the Great Oolite of 

 Minchinhampton, in the greater width of its tesserse, and length of its rays. 



