> EXPLANATION OF THE PLATES. 33 
Carapoc.—‘ Common in the schists of the Caradoc or Bala limestone at 
several places near Bala, Merionethshire and Builth, Brecknockshire; also 
found in the shales of the Bala limestone, near Llanfyllin, Montgomery- 
shire; and south-east of Cerrig-y-Druidion, Denbighshire.” Brit. Sil. 
Brach., p. 80; and Mem. Geol. Surv., vol. iii., p. 266. In Ireland it is 
frequent in slaty beds of Caradoc age, near Grange Hill, Kildare ; occur- 
ring also in the hard calcareous beds of Grangegeeth, Co. Meath ; and the 
Caradoc shales of Frankfort, Co. Wexford ; and Newtown Head, Water- 
ford. Mus. G.S. I. 
Norr.—In reference to Mr. Davidson’s enumeration of the localities for 
this remarkable species, it may be desirable to observe that this fossil, and 
probably the specimens of Lingula ovata, noticed in his valuable mono- 
graph on British Silurian Brachiopoda, as having been collected at Car- 
rickanearla, Chair of Kildare, is not from the very fossiliferous limestone 
(equivalent of Caradoc-Bala beds) known as that of the Chair of Kildare, 
which is situated on Grange Hill, about three miles north of the town of Kil- 
dare ; but from a place near it, being found in distinct beds of a more shaly 
character (although believed to be of the same Caradoc age), a little east of 
the limestone knoll, known as the Chair, and at the base of the hill. From 
a third locality, about half a-mile north-east of the Chair, there are also 
shaly beds, but with a distinct set of Silurian fossils, considered to be the 
equivalents of Llandovery strata. me 
Fic. 6.—a, b, c. LEPTNA SERICEA, Sowerby. 
Silurian System, pl. xix., figs. 1, 2. . 
a. Original. Convex or ventral valve; in dark compact limestone, Lambay 
Island, Co. Dublin, Mus. G. S. I. 
b. Original. Portion of surface of fig. a, enlarged, showing the widely dis- 
tant and fine intermediate radiating stri. 
ec. Original. A group of small examples of the flat dorsal, with interior and 
exterior ventral valves, on a slab of Caradoc sandstone, full of these fossils ; 
from Cheney Longville, Shropshire. Mus. Geol. Surv. Ivel. 
LuaANpDEILO to Luanpovery and ? WENLOCK, is the range of this species 
given in Siluria, fourth edition, p. 525. At p. 194 of the same work are 
the following remarks: ‘“ Of the two species of Leptzna, which are preva- 
lent in the Lower Silurian Division, the most frequent is Z. sericea, which, 
occurring in swarms among the slates of Snowdon, is also most abundant 
and characteristic in the Caradoc sandstone of Shropshire.” In Ireland it 
is not uncommon in slaty Caradoc rocks, near Balbriggan; and in limestone 
at Portraine, and Lambay Island, Co. Dublin ; as well as at several locali- 
ties in rocks of the same age in Wicklow, Wexford, Waterford, and Tyrone. 
Fic. 7.—a, b,c. OrtHIs ACTONIA, Sowerby. 
Silurian System, p. 639, pl. xx., fig. 16; Brit. Sil. Brach., pl. xxxvi., figs. 
5-17. 
a. View of both valves. From Mem. Geol. Surv., vol. iil., pl. xxi., fig. 7. 
b. Profile view ; showing relative position of valves. bid., fig. 8. 
c. Interior of flat (dorsal) valve. Jbid., fig. 6. 
LiANDEILO to LuaNpovery. Sil., fourth edition, p. 526. Abundant in the 
Llandeilo and Caradoc rocks of Shropshire, Wales, and Ireland. Llandeilo 
Flags, Garn, Arenigs; Caradoc, Bryn Bedwog, near Bala, &c. (Davidson). 
