Chap. VI.] 
WENLOCK FOSSILS. 
121 
species Periechocrinus moniliformis, PI. XIII. f. 1, 2, is the most charac- 
teristic ; it covers large surfaces of the limestone at Dudley, and is found 
in disjointed fragments in many other localities. 
Among the Mollusks of this formation, which are figured in Plates XX. 
to XXXIII., Orthoceratites are very abundant, Orthoceras annulatum and 
0. Brightii being frequent species. Bellerophon dilatatus, B. Wenlock- 
ensis, and the singularly beautiful Conularia Sowerbyi, PI. XXV., are charac- 
teristic. Among the most frequent spiral shells are five species of Euom- 
phalus, viz. E. carinatus, E. sculptus, E. discors, E. funatus, and E. rugosus 
(Plates XXIV., XXV.). 
Ordinary Bivalve Shells are less common ; but Orthonota cingulata, Avicula 
reticulata, Pterinea retrofiexa and Pt. planulata, the last figured in Chap. X v are 
abundant species. Of Brachiopods, Strophomena euglypha, S. filosa, and espe- 
cially S. depressa, Pentamerus galeatus, Spirifer plicatellus (S. radiatus and 
S. interlineatus, Sil. Syst.), S. trapezoidalis, S. crispus, and S. elevatus, Orthis 
rustica, 0. elegantula, arid 0. hybrida, Leptsena transversalis and L. laevigata*, 
are all described in the ' Silurian System.' With them are Atrypa reticularis 
and A. marginalis, besides several plaited Terebratulidse, of which Retzia cuneata, 
PI. XXII., and R. Salteri, Davidson, are often plentiful ; but the Rhynchonella 
borealis (Terebratula lacunosa of my old work) is by far the most common 
species. Rhynchonella Wilsoni and a small variety of R. nucula are also some- 
times abundant (see PI. XXII. and woodcuts in Chap. X.). 
Trilobites are very common ; the most frequent of them is the Calymene 
Blumenbachii, formerly called the 'Dudley Locust' (PI. XVIII.), a species 
which, as we have seen, also occurs deep in the Lower Silurian rocks, and, 
as we shall presently find, ascends also into the Upper Ludlow. 
Other forms of these creatures are also prevalent ; a few may be noticed. 
Encrinurus punctatus and E. variolaris, figured in Chap. X., are very common 
in both the limestone and the shale. Phacops Downingiae is one of the most 
characteristic Trilobites, particularly in the environs of Dudley. Phacops 
Stokesii (Calymene macrophtkalma of my former work), Ph. caudatus, Acidaspis 
Brightii, and Cheirurus bimucronatus (see Pis. XVIII. & XIX.), are frequent fos- 
sils, and, as before stated, belong also to inferior formations. Phacops caudatus is 
especially abundant in the Malvern Hills ; whilst Calymene Blumenbachii is 
the reigning fossil at Dudley. Bumastus Barriensis and Homalonotus delphino- 
cephalus, which have been cited from the Lower Wenlock or Woolhope lime- 
stone, are also found in this rock, the former very frequently. The Annelides 
Cornulites serpularius and Tentaculites ornatus occur on almost every specimen 
of the limestone at Dudley. 
In the above mentioned districts, the Wenlock limestone passes upwards 
gradually into a thick mass of pale-coloured shale, undistinguishable from 
that beneath the solid rock. From the physical relations of this shale, 
and from its forming usually a part of the same hills as the mass of the 
Ludlow rock, it is classed with that formation, though the reader must 
understand that in reality it is only an intermediate band intimately 
* See Plates XX. to XXII. 
