from the Island of Malta. 107 



Bonifacio in Corsica, and has given an account thereof in a 

 letter addressed to Prof. Constant Prevost ; the following abstract 

 relating thereto will be read with interest : — 



" We shall quit now," says M. Colloinb, " the eruptive rocks, 

 and transport ourselves to the south, at Bonifacio, where we 

 have remained some days, to go and see the bed of fossil Urchins. 

 They are found in a fragment of limestone completely enclosed 

 in the granite. Bonifacio is built upon a high escarpment of 

 this limestone, formed of horizontal beds having a coarse struc- 

 ture, full of the fragments of shells, the species of which were 

 indeterminable. This escarpment is incessantly beaten and 

 demolished by the action of the wind and the sea. Upon all 

 this coast the beds overhang, and are worn into caverns by the 

 inroads of the sea. 



" The bed of Urchins is situated at some leagues to the north- 

 east of Bonifacio, towards the roadstead of Santa-Manza, at the 

 limit of the granite. The escarpment itself is here granitic, 

 and the Urchin limestone caps the granite. The bed which 

 contains the most beautiful specimens is only accessible by 

 means of a laddei', and their extraction is difficult." 



The Calcaii'e k Oursins is only found in three localities in 

 Corsica, at Bonifacio, at Aleria, and at Saint-Florent, and 

 always in small detached beds of inconsiderable extent, which 

 do not extend into the interior of the island. The deposits of 

 Bonifacio and Saint-Florent were the only ones visited by M. 

 Collomb*. The rock is a light-coloured limestone, sometimes 

 white and soft, or hard and cherty, and contains an abundance 

 of small quartz pebbles derived from the decomposed granite. 



B. Description of the Fossil Maltese Echinodenns. 

 Cidaris Miletensis, Forbes MSS., n. sp. PI. IV. fig. 1 a-c. 



Test oblately spheroidal, much depressed at both poles; am- 

 bulacral areas undulated, depressed in the centre, with an 

 elevated marginal row of close-set tubercles on each side of 

 the areas ; poriferous avenues of the same width as the areas ; 

 interambulacral areas rather prominent, with two rows of 

 primary tubercles, about sLx in each row ; mammillary emi- 

 nences large, each with a circle of boundary granules ; spines 

 nearly the diameter of the test in length, tapering from the 

 base to the apex ; mouth-opening very large. 



Dimensions. — Height j^ths of an inch ; transverse diameter 

 l/o inch. 



* Bull, de la Soc. Geol. de France, torn. xi. p. 67 ef seq., 2 serie. 



