GONI ASTER. 31 



these plates are pitted all over, indicating that they were covered by minute polygonal 

 granules. The marginal plates were exceedingly numerous, and towards the extremities 

 of the rays became so approximated, that the rows of each side of an arm nearly or quite 

 touched. The under-surface was covered by large punctated flat polygonal ossicles closely 

 set, and along the margins of the avenues are stouter and more convex ones that bore short 

 spines and were grooved. Towards the slender extremities of the arms these occupy all 

 the space between the marginal plates. 



Fine fragments of this star-fish are preserved in the Museum of Practical Geology, 

 to which they were presented by Mr. Charles Stokes, and in the cabinet of Mr. 

 Bowerbank. 



2. GONIASTER MARGINATUS. Plate IV, fig. 4. 



GoNiASTEK MARGINATUS, Forbes. Mem. Geol. Surv. Great Britain, vol. ii, pt. 2, p. 475 ; 

 and Fig. and Descr. of Brit. Org. Remains, dec. i, pi. iii, fig. 2. 



The only known fragment of this star-fish is the one described in the first decade of 

 'British Organic Remains,' and procured by Mr. Charles Stokes from the London Clay of 

 Sheppey. 



It consists of five superior, and as many inferior marginal plates. The upper ones are 

 large, oblong, regularly declining on their outer sides, and of comparatively little altitude. 

 Their surface is but slightly convex, thickly punctured all over, and bordered laterally by a 

 distinct elevated rim. The inferior plates are similar, but have even more elevated margins, 

 and the rim is continued on them across their outer sides. The dermal ossicles are small 

 and punctate. The length of the fragment is three eighths, and its breadth less than two 

 eighths of an inch. 



3. GoNiASTER TUBERCULATUS. Plate IV, fig. 5. 



In the Museum of Practical Geology there is a fine fragment of a ray, which, whilst it 

 resembles in many particulars Goniasfer Stokesii, exhibits characters that entitle it to be 

 regarded as a portion of a distinct species. The part preserved measures one inch and four 

 tenths in length, by one inch three tenths in breadth at its base, and seven tenths of an 

 inch towards its extremity. The dorsal surface appears to be covered by small irregular 

 ossicula. The margin is flanked by two series of nearly equal cuboidal plates, with steep 

 sides, and slightly rounded summits ; these are remarkable for bearing a large areolated 

 tubercle, one on each, at their obtuse external edges. These tubercles are larger on the 

 upper than on the under plates. The whole surface of each plate, except the tubercle, 

 is closely pitted, and on some are preserved the small closely-set polygonal granules that 

 occupied the pits. The dermal ossicles of the ventral disk are rather large. The avenues 

 are bordered by strong square plates, bearing short, obtuse, stout spines. 



