MR J. W. GREGORY ON THE MALTESE FOSSIL ECHINOIDEA. 637 



this bed from the underlying limestone, and its stratigraphical relations also show the 

 intimate relations between the two. Dr Murray * describes the Blue Clay as being 

 35 feet thick in some places, while elsewhere it is wholly wanting, and sometimes a 

 gradual transition can be traced from the clay into the limestone. It would thus appear 

 to represent merely a local argillaceous phase of the Globigerina Limestone produced 

 during the elevation of the Maltese area into the shallower zones in which the later 

 formations were laid down. 



The equivalents of the Globigerina Limestone, with its overlying cap of Blue Clay, 

 may then be tabulated as follows : — 



Corsica. Malta. VienDa Basin. Series. 



_ . _ . , ., . ( Lower Globigerina Limestone, (Sotzka Schichten), Aquitanian. 



Zone a Pecien oonifaciensis, . < TT 1_ ' 



t U PP er " » M Horner „ } Langhian . 



Zone a Peden cristatus, . . Blue Clay, J } Schlier, I 



Zone a Cerites et Pleurotomes, Greensand, Grander Schichten, } Helvetian. 



It seems only by the recognition of the dual affinities of the Globigerina Limestone 

 Echinoidea that one can explain the association of two groups of species having characters 

 of the faunas of different depths. The Corsican species and their allies are a set of 

 forms that might be expected on the deeper slopes at a little distance from the mainland, 

 while the small elongated Echinolampas, the Studeria, the thin -tested fragile Sarsella 

 anteroulta, and the ethmophract Hemiaster vadosus, indicate a much greater depth. 

 There is nothing so truly abyssal as the Cleistechinus described by M. de Loriol t from 

 the Tuscan Schlier, but the whole facies of this latter group of Maltese species has a 

 deep-sea aspect. The occurrence of these two groups of Echinoidea in the same deposit 

 appears to indicate that Malta was on the border-line between two parts of the Mediter- 

 ranean basin which had a different physical history. It seems that the Maltese area 

 must have undergone alternate elevations and depressions. With the former, the shallow- 

 water types from the north-west entered the district, and were supplanted by species 

 from the deeper eastern sea as subsidence again set in. When the elevation became 

 permanent, the deeper forms finally left the Maltese area and survived only in the 

 deeper seas of the Adriatic. 



These considerations therefore suggest that, instead of the deep-sea deposits of the 

 Globigerina Limestone of Malta, the Langhien of Liguria, the Schlier of Vienna, the Zone 

 a dents de poissons of Corsica, the Black Clay with Meletta of Southern Russia, &c, 

 being on one horizon, and representing a period of regional submergence, they mark only 

 a series of local subsidences of basins which in the main were isolated from one another 

 by areas of shallow sea. Thus may be explained the high proportion of peculiar species 

 in each of these limited areas, while the general resemblance of the faunas may be due 



* Op. cit, pp. 465, 466. 



t " Description des Echinides des environs de Camerino (Toscane)," Mem. Soc. Phys. Hist. Nat. Geneve, xxviii., 

 No. 3, 1882, pp. 27-30, pi. i., f. 12-14. 



VOL. XXXVI. PART III. (NO. 22). 5 D 



