DESCRIPTIVE REMARKS, XXXV 
have commenced in this formation ranging up through all the overly- 
ing Silurian groups. JMeristella angustifrons, Plate xiv., fig. 9, and 
Rhynchonella angustifrons, fig. 10, are remarkably abundant, particu- 
larly in the equivalent rocks of Ireland and Scotland. Of Strophomena 
ten species are recorded from these strata; one of them, S. compressa, 
fig. 6, occurring in the upper beds and the overlying Wenlock forma- 
tion ; S. depressa, plentiful in Wenlock strata, amongst the fossils of 
which formation it is figured (Plate xx., fig, 9), and S. antiquata are 
frequent in the Lower Llandovery; S. euglypha, also a common Wen- 
lock fossil (Plate xx., fig. 8), being more scarce. Several species of 
Leptena, including the well-known Lower Silurian fossil, LZ. sericea 
(Plate xi., fig. 6), and LZ. transversalis (Plate xiv., fig. 7), as well as 
Orthis calligramma (Plate xi., fig. 9), and O. elegantula figured with the 
Wenlock fossils (Plate xx., fig. 7), are not unfrequent in the Llandovery 
rocks. Pentamerus, including Stricklandinia, are the most characteristic 
fossils of the class in these rocks, both in Shropshire and South Wales ; 
they are so numerous as to have given the name of Pentamerus rock or 
limestone to the zone in which they occur; five or six species of these 
remarkable shells are known, four of the most typical being represented 
on Plate xv. 
Brvatye Suetzts.—Conchifera, are not unfrequent; thirty species of 
these are recorded, belonging, for the most part, to the Mytiloid and 
Aviculoid groups; a species referred to the recent genus Mytilus (Plate 
xvi., fig. 1), one also of Modiolopsis, six species of UOrthonota, and seven 
of Pterinca ; the small Anodontopsis bulla, fig. 2, and other shells with 
hinge teeth resembling the recent Wucula, are common at Malvern; 
Ctenodonta Eastnort (fig. 3) and C. lingualis are typical fossils showing 
this character. 
NIVALVE SHELLS.— Gasteropoda, are slightly in excess of the con- 
chiferous bivalves, thirty-four species being catalogued from these 
strata; five of them belong to Hwomphalus ; a similar number to the 
more elongated spiral shells Holopella, a typical form, H. cancellata, 
being represented on Plate xvi., fig. 5 (this shell is alluded to in 
Siluria, 4th ed., p. 212, as ‘‘ our largest British species, often three 
inches long, common to the Lower and Upper Llandovery’’); eight to 
Murchisonia, a characteristic genus named in honour of Sir R. Mur- 
chison, which is also an elongated many-whirled shell, allied to Pleu- 
rotomaria, and peculiar to Paleeozoic strata, ranging from the Llandeilo 
to the Ludlow formations inclusive, of the lower division, and continuing 
through the Upper Paleozoic strata into the Permian. MM. angulata 
(fig. 6), alarge spiral shell, with another and still larger species; J/. Prycez 
(Siluria, 4th ed., Pl. x., fig 11) occurs throughout the Lower Llandovery 
rocks of Wales. A flattened trochiform shell, Raphistoma lenticularis 
(Siluria, 4th ed., Pl. x., fig. 10), also allied to Pleurotomaria, is said to 
be of frequent occurrence in Llandovery rocks; zbid., p. 212. A shell 
with seven or eight whirls resembling in shape the recent top shell, 
Trochus, is doubtfully referred to that genus by the name of 7. multe- 
