XXX Yl DESCRIPTIVE REMARKS. 
torquatus (fig. 7); it is very plentiful in the Upper Llandovery rocks of 
Galway, and is believed also to occur in Ayrshire and Pembrokeshire. 
Of Bellerophon as many as eight species are already enumerated 
from these strata; one of these, B. trilobatus (Pl. xvi., fig. 8), is selected 
as a small species, commencing in Llandovery strata, and ranging up- 
wards to the Ludlow and Tilestone series ; it occurs both in Gloucester- 
shire and Galway. 
Two kinds of a thin curved discoidal shell, with widely separated 
whirls, named Heculiomphalus and Conularia Sowerby? (Siluria, 4th ed., 
Pl. xxv., fig. 10), a Pteropod which commences in the Caradoc, ranges 
through the intermediate strata to the Ludlow rocks. 
Crenaorop shells, although not numerous in this formation, are 
present in considerable variety ; of the straight forms, as in Orthoceras, 
several species have been collected; one of these, O. subgregarium 
(Plate xvi., fig. 11), is found with others in the Llandovery rocks of 
Galway. A curved shell of this class, Cyrtoceras approximatum, repre- 
sented on the same Plate, fig. 9, is, like the preceding one, confined to 
Llandovery rocks. A coiled discoidal shell, Letwtes cornu-arvetis, fig. 
10, found in the lower division of these rocks, is also a Caradoc species, 
and an example of the extreme variability in form of the shells of this 
class of the Mollusca. 
Fossils referred to the ANNELIDA are not uncommon at certain loca- 
lities, being most plentiful in the strata of the upper division. The 
prevalent species is Zentaculites Anglicus, a small fossil figured with 
those of the Caradoc (Plate x., fig. 3), in which formation, as in Llan- 
dovery strata, it occurs in considerable abundance. 
Of TritosrTEs the most frequent is Encrinurus punctatus (Plate xvi., 
fig. 12). Calymene Blumenbachii (included with the Wenlock fo8sils) 
is not uncommon ; few species are, however, peculiar; certain Lower 
Silurian forms range into these rocks, such as l/lenus Bowmanni, figured. 
with the Caradoc fossils (Plate xii, fig. 5), and Lichas laxatus, which 
is also a Caradoc species; Phacops Stokesv and the characteristic P. 
caudatus, with others, being Upper Silurian types, first appearing in 
this formation. 
