XXXIV DESCRIPTIVE REMARKS. 
Silurian fossils predominate; thus forming a connecting link between 
the two great divisions of Silurian strata, clearly proving it to be one 
continuous series of deposits, 
From the difficulty ofselecting species sufficiently distinct to charac- 
terize the lower and upper members of this formation, it has been found 
necessary to include them all in the same Plates (xiv. to xvi.). In the 
explanation to these Plates, where practicable, the position each fossil 
occupied in the series is however mentioned. 
Graprouites, the alliance of which with the Hydrozoa is now the 
received opinion, so abundant in the argillaceous slates of the older 
rocks, are rare in these sandy strata; and, excepting G. priodon, Pl. 
xix., fig. 1, a species which ranges from the Caradoc to Ludlow strata, 
are entirely absent. 
Corats are not uncommon; the most plentiful consist of a few well- 
known species which, commencing in Lower Silurian strata, continued 
on during the formation of these deposits into that of the Upper Silurian, 
such as Fuvosites fibrosus, figured amongst the Caradoc fossils, Pl. x., 
fig. 1. #. Gothlandicus, Pl. xvii., oe 3 2; Halysites catenularius, fig. 3 
and Heliolites interstinctus, fig. 1, also on the same Plate, and all 
included with the Wenlock fone, as being most characterstie of that 
period. The simple turbinated corals called Petraia are the most 
abundant and characteristic of the class in these deposits ; as before 
remarked, in alluding to the fossils of the Caradoc rocks (ante, p. xxvi.), in 
accordance with the views of the eminent authors of British Fossil 
Corals, the proper position for these fossils, which are mostly internal 
casts, is with Cyathophyllum, to which genus I have referred them. 
There are eight species of Petraia included in the list of British Silurian 
fossils from Llandovery strata (Siluria, 4th ed., p. 511). Some of these, 
however, appear to me identical with P. elongata (Plate xiv., fig. 1, 
a, 6, c), particularly P. subduplicata, and probably P. bina; this will, 
I think, be evident on comparison with the figures from the same slab 
of P. elongata, showing different ages and conditions of this coral. 
EcuHINoDERMATA are comparatively rare either as Cystideans or 
Crinoids, except disconnected stems and joints; no entire specimens have 
yet been collected from these strata. 
Poryzoa are also poorly represented in these rocks; the species known, 
three only, all belong to Pélodictya, a genus more numerous in species 
during the preceding Caradoc formation ; one of the most frequent of 
these being figured on Pl. x1., fig. 2. 
Of all the fossils occurring in Llandovery strata Bracutopop shells 
are in the greatest profusion; Lingula parallela, Pl. xiv., fig. 2, and 
L. crumena, fig. 3, are examples of a genus at present existing on the 
shores of the Indian Ocean. Atrypa hemispherica, fig. 5, a species 
confined to Llandovery beds, abundant in the Abberley, Tortworth, 
and Malvern districts, but rare in Wales, is also the common fossil in 
the Upper Llandovery rocks of Galway, and the equivalent rocks of 
Scotland. Atrypa reticularis, frequent in the Wenlock formation, 
amongst the fossils of which it is figured (Plate xx., fig. 4), appears to 
