44 
SILURIA. 
[Chap. III. 
With the Lingulae (or Lingulellge), of which L. Davisii* is most abundant 
(L. lepis being rare), there are associated in the lowest courses of these 
flags several other fossils, of which Agnostus princeps is much the most 
Fossils (6). Lingula-flags, North Wales. 
2. Paradoxides Hicksii, 
Salter, from near Dol- 
gelly, North Wales. 
frequent, a similar form (A. pisiformis) being characteristic of this same 
band in Bohemia and Scandinavia. To the eye of the field-geologist, this little 
Crustacean seems to be scarcely distinguishable from the Agnostus of the 
overlying Llandeilo -flags (PI. III. fig. 8), in which deposit, as will presently 
be seen, there is a similar association of Lingula and Agnostus. L. Davisii 
and A. pisiformis are the common species in the Lingula-flags. The other 
fossils above quoted (Paradoxides and Olenus) are rare in Britain f. 
In the recently published volume (iii.) of the Memoirs of the Geological 
Survey, by Professor Eamsay, Mr. Salter has described at some length, in 
the Appendix, the various fossils of the two stages of the Lingula-flags, and 
has stated that Agnostus princeps (the English equivalent of the A. pisiformis 
of Sweden) occurs in millions, with a new species of Olenus, in the lowest 
of these. He has also shown the exact place of the Paradoxides of which 
the locality was unknown when the last edition of ' Siluria' was published. 
This fossil has been found both at Dolgelly and in Pembrokeshire, at about 
one hundred feet above the lowest black Lingula-slates. The Hymenocaris 
has also been found abundantly. Now, as in these deposits the Orthis 
lenticularis of Dalman, a wide-spread Silurian fossil, is also found abun- 
dantly with Lingula and Agnostus, we see how difficult it is to separate 
these strata in general classification from the rest of the Silurian rocks. 
* This little Brachiopodous Shell has often been Boheme et de Scandinavie,' by M. Barrande, in 
so much affected by the pressure to which the which that author shows the exact parallelism of 
schistose and cleaved rocks abounding with it all the beds of the Silurian basin of Bohemia with 
have been subjected, that it has assumed the form those of Scandinavia, as indicated in the ' Ke- 
of several distinct genera, such as Tellina, Modi- giones' (or Stages) of M. Angelin. By reference 
ola, and other Bivalve Shells. to the existing distribution of submarine animals, 
t See Angelin's ' Palaeontologia Scandinavica,' he satisfactorily explains why the species of Crus- 
Pars I. taceans and other animals, detected in Silurian 
Geologists who desire to consult a clear and tracts not distant from each other (the strata of 
comprehensive view of the equivalents of the which were simultaneously accumulated), often 
British zone of the Lingula-flags, as well as the differ, though the generic types agree. This in- 
whole group of the Silurian rocks, as exposed in teresting topic, bearing on the ancient hydro- 
Bohemia and Scandinavia, should read a memoir graphy of Europe, wilf be considered in a suc- 
entitled 'Parallele entre les Depots Siluriens de ceeding Chapter. 
