268 Dr. T. Wright on Fossil Echinoderms 



the test ; the lateral pair have a regular tuberculatiou, 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^. eurynotvs ; 

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

 general tumidity of the sides distinguish it from S. 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 vertex, 

 which is nearly central ; petaloidal portions of the ambulacra! 

 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. 



Dimensions. — Antero-posterior diameter 5y^^ inches, trans- 

 verse diameter 5y% inches, height 2^^ inches. id 



Description. — This large Clypeaster has been mistaken for one 

 of the varieties of C. altus, but a careful study of its test dis- 

 closes characters by which it is readily distinguished from that 

 common form. The circumference is nearly pentagonal ; it is 

 rounded before, undulated on the sides, and nearly straight 

 behind ; the sides of the pentagon are of unequal length, those 

 forming the front of the test are the shortest, those of the 



