DESCRIPTIVE REMARKS. xli 
the Pentland Hills, near Edinburgh, the fossils exhibit clear evidence 
as to the Upper Silurian character of the deposits, representing, in all 
probability, a Wenlock, surmounted by a Ludlow series. 
‘In Ireland, Upper Silurian rocks, abounding in typical Wenlock 
and Ludlow fossils, occur in the Dingle promontery, county Kerry, 
and in occasional tracts in the counties of Galway and Mayo. 
Although certain fossils, by their abundance, larger proportions, or 
other peculiarities, may be said to characterize some of these subdivi- 
sions, the whole assemblage agree so much in general character as to 
render it difficult to select a series of typical forms for each; the cha- 
racteristic fossils for each group of strata are therefore combined, those 
of the Wenlock rocks being illustrated on Plates xvii. to xxiii. ; those of 
the Ludlow rocks on Plates xxiv. to xxvil., both inclusive. 
In the Woornorr Limestone at Woolhope, amongst the principal 
fossils are the Trilobites Momalonotus delphinocephalus, Plate xxiii., 
fig. 7; Illenus Barriensis, the Barr Trilobite, fig. 4, and Phacops cauda- 
tus, fig. 5; The Annelide Cornulites serpularius, Plate xix., fig. 2; 
Brachiopod Mollusca, Orbiculovdea Forbesii, fig. 7; Spirifera elevata, 
Plate xx., fig.2; Atrypa reticularis, fig. 4; Strophomena depressa, 
fig. 9 ; Rhynchonella Wilsini (figured with the Ludlow fossils), Plate 
XX1., fig. 8), and less frequently Orthis elegantula, Plate xx., fig.7; also 
the Cephalopod, Orthoceras annulatum, Plate xxii., fig. 4. Siluria, 4th 
ed, p- Lid. 
Wentock Suate.—tThe fossils of this stratum are generally similar 
to those of the overlying limestone; the prevailing forms, exclusive of 
Corals and Trilobites, which are chiefly of species unknown in the lower 
deposits, are Brachiopods, of the genera Leptena, Orthis, Strophomena, 
Atrypa, and Rhynchonella ; among them are several common to this de- 
posit and the Lower Silurian rocks, such as Orthis elegantula, Pl. xx., 
fig. 7; Strophomena depressa, fig. 9; Atrypa reticularis, fig. 4; Spiri- 
fera plicatella, fig. 1; Meristella tumida, fig. 3, &e. Most of these 
Lower Silurian forms have a much greater vertical range, continuing 
upwards through the Wenlock high into the Ludlow formation. Odolus 
Davidsoni, a species recognized by Mr. IT. Davidson in the Wenlock 
shale, also occurs in the limestone, and is recorded in “ Siluria” as a 
Llandovery fossil. Avicula, Ctenodonta, and some other bivalve shells, 
occur frequently; but few of them are characteristic, except Cardiola 
interrupta (figured with the Ludlow fossils), Pl. xxv., fig. 5. Of the spiral 
or univalve shells, Kwomphalus funatus, Pl. xxi., fig. 9; E. alatus, 
fig. 7; Acroculia haliotis, fig. 12; and of Heteropods, Lellerophon Wen- 
lockensis, Pl, xxii., fig. 2, with B. delatatus, fig. 1, are the most common. 
Pteropoda are not so plentiful as in the lower rocks. Zheca Forbesii 
(figured with the Ludlow fossils), Pl. xxvi., fig. 6, and Zheca anceps, 
Pl. xxii., fig. 3, are Wenlock shale species. Amongst the Cephalopoda, 
Orthoceras annulatum (previously cited), Pl. xxii, fig. 4, O. filosum, 
and O. angulatum (figured in ‘ Siluria)’ are rare; but many of the 
smooth and thin-shelled species, such as O. swbundulatum, O. primevum, 
&e., are frequent in these muddy sediments; they are almost the 
