Chap. X.] 
UPPER SILURIAN TRILOBITES. 
235 
remarkable for having the lobes of the head nearly obliterated, and possessing 
two large neck-spines. The common Calymene Blumenbachii, PI. XVIII. f. 10, 
was perhaps the most prolific of all the Silurian Trilobites, and is, as before 
stated, known also in the lower division of the system. C. tuberculosa, PL XVIII. 
f. 11, and Foss. 64. f. 2, which was formerly given as a variety of it, is a very 
plentiful species in the Wenlock Shale. 
Among the Trilobites here figured which were not published in my former 
work, Sphserexochus mirus, Foss. 65. f. 1, is singularly formed, the head being 
so inflated as to resemble a ball. This Wenlock fossil has a very general geo- 
graphical or horizontal range, being found both in America and Bohemia in 
Upper Silurian rocks. It appears, however, to have existed earlier in Britain 
than in those distant parts ; for it is found in the equivalent of the Caradoc rocks 
in Ireland. Four or five species of Lichas (a genus already figured in Chap. IX.) 
are now known in Wenlock Limestone. The genus is remarkable for the shape 
of the head and its lobes. L. Grayii, L. Salteri, L. Barrandii, Foss. 64. f. 3, and 
L. hirsutus are all species figured and named by Messrs. Fletcher and Salter from 
Mr. Fletcher's rich collection (Quart. Journ. Geol. Soc. vol. vi. p. 235). With 
Fossils (65). Wenlock Limestone Trilobites. 
1. Sphserexochus mirus, Bey rich ; 
with a coiled-up specimen. 2. Cyphas- 
pis megalops, M'Coy. 3. Phacops 
Downingise, Murch. ; both extended 
and coiled-up. 4. Cheirurus bimu- 
cronatus ; and its labrum or lip. 5. 
Encrinurus punctatus, Brim. ; and its 
labrum ; drawn from a Dudley speci- 
men. 6. E. variolaris, Brong. 7, 
Proetus latifrons, M'Coy. 8. Aci- 
daspis Brightii, Murch. 9. A. Bar- 
randii, Fletcher and Salter ; the head or 
cephalothorax. 
them is associated a small and very common species, the L. (Arges) Anglicus 
of Beyrich, Foss. 64. f. 1, of which a very imperfect illustration was formerly 
given in Brongniart's work, from a Dudley specimen. It occurs also in Upper 
Ludlow rock, in the WhitclifFe, Ludlow. Phacops Downingise (Foss. 65. f. 3, 
and PI. XVIII. f. 2-5), and P. caudatus, PL XVIII. f. 1, with its variety, P. 
longicaudatus, PL XVII. f. 3-6, have been already quoted (p. 121) as very 
common forms. 
Proetus Stokesii, PL XVII. f. 7, and P. latifrons, Foss. 65. f. 7, are also far 
from rare in Wenlock strata. Bumastus Barriensis, Murch. (Illsenus, auct.), 
Foss. 17. p. Ill, and PL XVII. f. 9-11, ranges, as before said, from the lowest 
Wenlock beds to near the top of the Upper Silurian. This fine fossil occurs of 
the largest size in the Woolhope Limestone, and is found in the pipeclay beds of 
that formation at Malvern. Two species of Homalonotus also have been already 
quoted, pp. Ill, 133 ; H.Knightii, Konig, being very characteristic of the Upper 
Ludlow rock. 
Cyphaspis megalops, M'Coy, Foss. 65. f. 2, and a small species, C. pygmeeus, 
Salter, are the only species of that genus known in England. The former began 
life in the Lower Silurian epoch. Deiphon Forbesii, Barrande, is a rare, globular- 
