DESCRIPTIVE REMARKS. ; XXX1 
Qnd ed., pl. Lxiii., figs. 1, 2, to which it is closely allied, being included 
in the same family Escharide. 
To illustrate this group of fossils, which are formed of a number of 
cells arranged in several series and of various shapes, the small wood- 
cut, fig. 10, reduced from Busk’s Polyzoa (Pal. Soc.), will serve to show 
the normal form of a cell with its orifice or aperture 
and lid. The margins of this opening, from which the Fg. 10.—Cell 
“‘ polypes”’ protrude in the living examples, are either 9fPolyzoan (after 
smooth, provided with spines, or valvular. Busk). 
Bracuropopa are the most numerous of the Mol- 
luscan shells in Caradoc strata; characteristic forms 
of Lingula, Discina, and Crania, are represented on 
pl. xi., figs. 3,4, and 5. Leptena sericea, fig. 6 of 
the same plate, a common fossil throughout Lower 
Silurian strata, is most numerous in strata of this for- 
mation. Orthis Actonie, fig. 7, characteristic also of 
the Llandeilo rocks, O. flabellulum, fig. 8, and O. calli- 
gramma, especially the latter, is remarkably abundant 
in Caradoc rocks, as also is Strophomena expansa, Pl. « Cell. 
:: 6. Orifice or aper- 
Mil., fig 1; ‘ie 
ConcutFera, or ordinary bivalve shells, are less 
numerous in these older strata, except in special localities; Modzolopsis, 
Pl. xii., figs. 2 and 8, resembling the recent Modiola; and Ctenodonta, 
fig. 4, small shells with hinge teeth, like the recent Nucula, are examples 
of some of the most frequent. 
Gasteropopa.—Univalve shells are still fewer in the number of 
species, although some of them, such as Holopea concinna, fig. 5, and 
Murchisonia turrita, fig. 6, abound in strata of this age at certain loca- 
lities in Ireland; the former species, although resembling much the 
recent Natica, is believed to represent the Ianthine, or oceanic floating 
snails; and MMurchisonia, the Pleurotomarie of Upper Paleozoic and 
secondary strata, and the recent Cerithia with notched apertures. 
Of the Nucrroprancurata, univalve shells resembling the nautilus 
in external form, but without possessing air chambers, eight species are 
recorded from Caradoc strata. Bellerophon bilobatus, fig. 7, 18 a com- 
mon fossil of this formation in Britain, being ‘‘ equally characteristic 
of the same deposits in North America, Spain, and Bohemia.—Sil., 
4th ed., p. 198. : 
Theca reversa, fig. 9, is believed to be a Prerorop, with which the 
delicate shell of the recent Clio borealis offers a comparison. The fossil 
named ? Theca triangularis, fig. 8, and to which I have prefixed a query 
in the explanation of Plate xii., was figured by Portlock as a doubtful Or- 
thoceratite, and has since been referred to Theca. Having had the oppor- 
tunity of examining his original specimens, I have come to the conclusion 
that it is nothing more than the pointed termination of an Orthoceras, 
such as the species he figures from the same locality as elongato- 
cinctum or subundulatum ; it was unfortunately introduced into the 
Plate before I discovered it had characters incompatible with that of 
