4 Tate— List of Irish Liassic Fossils. 



number is reduced to 71. This has been increased during the last few years 

 to 189, all of which species are catalogued in List II. 



This list cannot be considered complete, inasmuch as additional species 

 have been found time after time, on the occasion of revisiting those sections, 

 which have yielded the greater number of the fossils, and which, consequently, 

 from past experience, will continue to reward a search by an industrious 

 collector. 



The principal localities in County Antrim are Colin Glen and Cave Hill, 

 near Belfast ; Whitehead, Island Magee, and Waterloo, near Larne ; Glenarm ; 

 between Garron Point and Red Bay ; Ballintoy. In County Londonderry, 

 Magilligan, Aghanloo, &c, whence Portlock obtained the majority of the 

 species of his catalogue. 



List No. II. shows the range of each species in the several members of the 

 Lias, as described by me in the Quarterly Journal Geological Society, Vol. xx., 

 p. 103 (1863) ; Vol. xxiii., p. 297 (1867) ; Vol. xxvi. (1870). 



The Liassic system is represented in the North of Ireland by the forma- 

 tions termed Rhsetic, Lower Lias, and Middle Lias. 



The Rhaetic series is as fully developed in the immediate neighbourhood 

 of Belfast as in any portion of Great Britain ; it is there capable of division 

 into the ' ' Avicula contorta-shales, " and the White Lias. Not more than 29 

 species have been satisfactorily identified from this formation ; 24 of these occur 

 in the lower zone, and 1 3 in the upper, whilst 5 of them pass up into the Lower 

 Lias. 



The Lower Lias, which I have divided into four zones or palaeontological 

 horizons, has yielded 151 species, 2 of which are common to the Middle 

 Lias. The " Planorbis Zone" has afforded 24 species ; two only, Gervillia 

 acuminata, and Mytilus subtilis, are confined to it, whilst the majority do not 

 extend upwards beyond the overlying zone. The " Angulatus-beds," relatively 

 rich in Gasteropods and Corals, have yielded 120 species, 26 of which pass 

 to the upper zones. The " Bucklandi-beds" have not been so thoroughly 

 searched as the lower zones, and I can only enumerate 21 species from them, 

 but 5 of these appear to be limited to this horizon. 



The Ballintoy, or " Belemnites acutus shales," have yielded 44 species. 

 They are comparatively rich in peculiar Cephalopods, and 19 species in all are 

 confined to this zone. 



The Middle Lias at Ballintoy contains sixteen species, two only of which 

 occur in the inferior beds. 



In the following table are indicated the number of species known and in- 

 ferred that pass from lower to higher zones, and the total number of species in 

 each member, of the Lias, and the per centage number of restricted species m 

 each member. 



