108 Dr. T. Wriglit on Fossil Echinodertns 



the sides by the fascicle, and above by the anal opening and 

 caudal process ; the base is convex ; the sternum is not very pro- 

 minent, and has lines of tubercles proceeding in radii from a 

 point near the border ; the basal portions of the posterior ambu- 

 lacra are naked, and around the mouth buccal pores are seen, 

 which extend at considerable intervals along the trajet of the 

 posterior pair. The mouth is situated in the anterior fourth of 

 the base and has a projecting under-lip ; the basal parts of the 

 interambulacra glide into the general convexity of the floor of 

 the test ; the lateral pair have a regular tuberculation, but on 

 the anterior pair the tubercles are larger and more irregular. 



Affinities and differences. The nearly central position of the 

 apical disc and the greater divergence of the antero-lateral am- 

 bulacra distinguish this Urchin from its congeners ; the narrow- 

 ness of the odd ambulacrum and the absence of the swelling-out 

 in the centre of the same, serve to separate it from S. eurynotus ; 

 the blunt caudal process, the small posterior border, and the 

 general tumidity of the sides distinguish it from $. Desori. 



Locality and stratigraphical position. Collected from bed 

 No. 4, the calcareous sandstone at Malta, where it is common ; 

 it is found likewise in the Molasse, middle tertiaries, of Mar- 

 tigues, Bouches-du-Rhone. Fine specimens are contained in the 

 British Museum, Jermyn Street Museum, and that of the Bristol 

 Institution. 



Since the preceding sheets of this memoir have been passing 

 through the press, we have had the opportunity of examining 

 the Maltese fossils belonging to the Geological Society, and some 

 that had escaped our notice in the British Museum collection ; 

 from these new materials the following notes are now added : 



Clypeaster Reidii, Wright, n. sp. 



Test large, broadly pentagonal, and much elevated; border 

 abrupt, margin thin and undulated, rising with steep sides at 

 angles of 60, and with a very little curve towards the verlex, 

 which is nearly central ; petaloidal portions of the ambulacral 

 areas large, nearly equal in width, and extending over nearly 

 three-fourths of the sides ; base quite flat ; mouth small, pen- 

 tagonal, nearly central ; basal ambulacral sulci proceeding 

 from the angles of the mouth, narrow, and sharply defined ; 

 anus round, near the posterior margin ; tubercles on the upper 

 surface small and closely set together, those on the base a 

 little larger ; apical disc nearly central and prominent, with 

 an outer circle of genital holes, and an inner circle of eye- 

 holes having the madreporiform tubercle in the centre. 



