MR J. W. GREGORY ON THE MALTESE FOSSIL ECHINOIDEA. 635 



than in the north, and thus it may in part have been synchronous with the Aquitanian ; 

 but it appears to be clearly homotaxial with the Lower Oligocene. That some consider- 

 able lapse of time intervened between this and the Upper Coralline Limestone is indicated 

 by the fact that when the same genera reappeared, with the return of the old conditions, 

 they were always represented by new species. 



The Upper Coralline Limestone does not contain many Echinoidea, but the Green- 

 sand (the Heterosteginakalk of Fuchs) yields a large number of Clypeasters. These may 

 be included in two species — Clypeaster altus and C marginatus. The former species is 

 represented by several well-marked varieties, such as C. pyramidalis, C. portentosus, 

 C. alticostatus, C. turritus, and C tauricus (?). The same species, with the same 

 varieties, are found in Calabria in the Helvetian, and they seem sufficient to determine 

 this horizon. Baldacci, moreover, has assigned the Heterostegina Limestone of Syracuse, 

 the Sicilian representative of the Greensand, to the Helvetian.* Two horizons may thus 

 be regarded as fairly settled, while the Upper Coralline Limestone may be readily 

 dismissed as the Tortonian, both from its superposition to the Helvetian and the agree- 

 ment of its fossils with those of the Leithakalk, as shown by Herr FucHS.t 



It is thus obvious that the Globigerina Limestone and the Blue Clay together 

 represent the Aquitanian (Upper Oligocene) and the Langhian (Lower Miocene); and no 

 doubt it would be very convenient to follow Fuchs in drawing the line between these two 

 systems at the change in the lithological character of the deposits. This change 

 Dr Murray J has shown to be due to some change in the physical conditions of the area, 

 whereby a larger proportion of clastic material was introduced into the sea in which 

 the higher deposit was being laid down. This is probably, as Dr Murray has said, 

 owing to elevation into a shallower zone. It is of interest to inquire whether this 

 alteration of level exactly coincided with the opposite change whereby the littoral and 

 land deposits of the Ligurian Aquitanians and the Viennese Sotzka and Eggenburg 

 Schichten were replaced by the deep-sea Langhians and Schlier. 



Herr Fuchs' conclusions as to the correlation of the Blue Clay and of the Globigerina 

 Limestone were based on 18 species of mollusca in the former, and on two in the latter. 

 The Echinoidea of the lower horizon, numbering 21 species belonging to 14 genera, 

 would appear to offer much better data. Of these species, 9 are peculiar to the Maltese 

 islands, and so are of little value, while, on the other hand, 4 species may be neglected, 

 as their range is so extensive both in time and space. Thus Schizaster parkinsoni, e.g., 

 lived from the Aquitanian to the Tortonian, and has been found from the West Indies, 

 on the one side, to Eastern Asia Minor, on the other. 



As a result of Herr Fuchs' identification of the Globigerina Limestone with the 

 Aquitanian, one is led to compare its Echinoids with those from this series in Italy. Not 

 one of the species occurs in the Aquitanian of Reggio, but that is possibly due to the fact 



* " Descrizione geologica dell' Isola Sicilia," Mem. descr. Carta geol. Italia, i., 1886, pp. 93, 108. 

 t Sitz. k. k. Ak. Wiss. Wien, lxx., Abth i , pp. 95, 96. 

 X Scott. Geogr. May., vi. p. 480. 



