160 BRITISH PALAZOZOIC FOSSILS. [CrusTAcga. 
very obtusely rounded, width rather more than twice the length, of three tumid lobes, the axis most 
convex and rather more than half the width of the side lobes, with eight strong rounded segments, lateral 
lobes with a narrow entire margin and seven strong rounded ridges, the first one or two of which shew a 
very fine mesial dividing line; length five lines. 
Position and Locality ——Caradoe sandstone, Alt yr Anker, Meifod, Montgomeryshire ; impure limestone 
of Capel Garmon, on the Cowney River, Denbighshire ; Wilfa, near Penmachno; Pont y Glyn, Diffwys, near 
Corwen ; (wm of the Cymmerig, Bala, Merionethshire, 
Explanation of Figures.—P1. 1. G. fig. 12. Cephalic shield, natural size, (angles not perfect in specimen), 
from Capel Garmon.—Fig. 13 and 14. Pygidium natural size, from Pont y Glyn, Diffwys. 
Puacors Downinaia (Murch. Sp.) 
Syn. and Ref—Calymene 1d. Murch. Sil. Syst. t. 14. f. 3. 
Sp. Ch.—Ovate, depressed, head and pygidium of equal length; cephalic shield rotundato-trigonal, 
flattened, slightly more than twice as wide as long, margin obtusely angulated in front, (lateral angles 
rounded) ; glabella very minutely and obscurely granulated, clavate depressed, anterior segmental furrows 
slightly sigmoid, oblique, second and third pair nearly transverse, all the furrows narrow and nearly reaching 
to the middle, the spaces behind the first pair are triangular, and broader than long, the second pair are 
transversely oblong, the space behind the third pair forms a nearly perfect transverse segment, only half as 
thick as the second space, or two-thirds that of the neck-furrow, which is very strong and prominent ; first 
seven rings of the thorax equal to the length of the head; pygidiwm semi-oval, length more than half the 
width, axis prominent, of seven thick segments, sides with five flattened duplex segments. Length one 
inch two lines. 
Neither the figures in the “Silurian System,” nor the “Memoirs of the Geol. Survey,” exhibit the 
intermediary or duplicating furrows on the lateral ribs of the pygidium, they however may be seen to exist. 
Position and Locality—Wenlock limestone of Dudley; Upper Ludlow of Benson Knot, Kendal; 
Moel Sessiog, Llanrwst. 
Sub-genus. OpontocuiLe (Hale and Corda.) 
Syn. = Dalmannia Emmerich, (not of Robineau-Desvoidy). 
Gen. Char.—General form, buckler, glabella, eyes and eye-lines, as in Phacops, but the lateral lobes of 
the glabella more equal; not contractile; thorax of eleven segments; plewripedes curved backwards and 
generally pointed at their extremities, facets very long, narrow rhomboidal, slightly defined ; pleural groove 
strong, slightly sigmoid and oblique (not angulated); pygidium elongate, generally pointed, axis with from 
twelve to twenty-two segmental furrows, sides with fewer (about half the number) strong ribs, usually duplex, 
confluent at their ends with the thickened entire margin; hypostoma with a dentate edge. 
This genus was first noticed by Emmerich under the name Dalmannia, which was used fifteen years 
before for a genus of insects by Robineau-Desvoidy, I therefore use the name of Hawle and Corda, who 
do not allude to Emmerich’s having previously characterised the genus. 
ODONTOCHILE CAUDATA (Brong. Sp.) 
Ref. and Syn.—Asaphus caudatus Brong. Crus. Foss. t. 2. f. 4, and Murchs SilSysteitenmenos 
Sp. Ch.—Ovate, cephalic shield depressed, semi-ovate, twice as wide as long, exclusive of the lateral 
spines, which extend backwards and a little outwards as far as the sixth or seventh segment, confluent at 
base with the thick strongly defined borders of the circumference and posterior margin; glabella broadly 
clavate, slightly angulated in front, coarsely and irregularly granulated, the anterior pair of segmental 
furrows broad, and inclining obliquely backwards and inwards, the two posterior pair much narrower and 
nearly transverse; eyes very large conico-reniform ; axal segments of the thorax four-fifths the width of 
