LONGMYND GROUP. 
485 
Fiff. 572. 
grounds, as the base of the Lingula Flags, but Messrs. Hicks 
and Salter, to whose exertions we owe almost all our knowl¬ 
edge of the fossils, have pointed out* that the most charac¬ 
teristic genera found in them are quite unknown in the Lin¬ 
gula Flags, while they possess many of the strictly Lower 
Cambrian genera, such as Microdiscus and Paradoxides, 
They therefore proposed to place them, and it seems to me 
with good reason, at the top of the Lower Cambrian under 
the term “ Menevian,” Menevia being the classical name of 
St. David’s. The beds are well exhibited in the neighbor¬ 
hood of St. David’s in South Wales, and near Dolgelly and 
Maentwrog in North Wales. They are the equivalents of 
the lowest part of Barrande’s Primordial Zone (Etage C). 
More than forty species have been found 
in them, and the group is altogether very 
rich in fossils for so early a period. The 
trilobites are of large size; Paradoxides 
Davidis (see Fig. 572), the largest trilo- 
bite known in England, 22 inches or near¬ 
ly 2 feet long, is peculiar to the Menevian 
Beds. By referring to the Bohemian tri- 
lobite of the same genus (Fig. 576, p. 488), 
the reader will at once see how these 
fossils (though of such different dimen¬ 
sions) resemble each other in Bohemia 
and Wales, and other closely allied spe¬ 
cies from the two regions might be added, 
besides some which are common to both 
countries. The Swedish fauna, presently 
to be mentioned, will be found to be still jjavidis. Salt, 
more nearly connected with the Welsh Menevian beds. st.Da- 
Menevian. In all these countries there vid’s and Doigeiiy. 
is an equally marked difference between the Cambrian fos¬ 
sils and those of the Upper and Lower Silurian rocks. The 
trilobite with the largest number of rings, Erinnys venulosa^ 
occurs here in conjunction with Agnostus and Microdiscus^ 
the genera with the smallest number. Blind trilobites are 
also found as well as those which have the largest eyes, such 
as Microdiscus on the one hand, Anopolenus on the other. 
LONGMYND GROUP. 
Older than the Menevian Beds are a thick series of olive 
green, purple, red and gray grits and conglomerates found 
in North and South Wales, Shropshire, and parts of Ireland 
* British Association Report, 1865, 1866, 1868, and Quart. Geol. Journ., 
vols. xxi., XXV.. 
