234 SILURIA. [Chap. X. 
by a form so like T. Anglicus, Salter, of the lower division, that it may pos- 
sibly be a variety only, in which case we gain another characteristic fossil for 
uniting the two groups. This Tentaculite is plentiful, like the Cornulite, in the 
sandy Ludlow rocks of Marloes Bay and Freshwater, Pembrokeshire. 
Other Annelides (Serpulites, Sil. Syst.) are very common in the Ludlow rock. 
They are flattened tubes, thick at each projecting edge, sometimes shelly, but 
at other times corneous, or even membranous on the sides. Serpulites longissi- 
mus, PI. XVI. f. 1, grew to a length of twenty inches, measured along its spiral 
curve. It is one of the type fossils which most attracted me when I first traced 
the range of the Upper Ludlow rock. Greyish-blue portions of it are found in that 
band over great distances throughout the Silurian region, and the small shining 
fragments are often mistaken for remains of Fish. Serpulites dispar, Salter, from 
Kendal, the tube of which has remarkably thin sides, is figured in the work 
descriptive of the Woodwardian Museum. Trachyderma coriaceum and T. squa- 
mosum of Phillips * are wrinkled tubes of these Annelides, frequent in the Ludlow 
rocks of the original Silurian region, and are occasionally found in an upright 
position in the. bed. A few other species are found in the Wenlock strata and 
the stratum which I formerly distinguished as the Fucoid-bed of Ludlow (p. 133). 
It appears to contain no remains of Sea- weed, but to be made up of the closely 
interwoven burrows of marine "Worms, and perhaps Crustaceans. 
The chief Crustacea are Trilobites. They are exceedingly abundant, form- 
ing in some beds, and especially in the Wenlock Limestone, the most conspicuous 
fossils. Many forms have been already quoted in the preceding Chapters ; and 
two woodcuts are here given, to represent either the principal forms not illus- 
trated in my original work or those now more perfectly known. Among the 
latter we may reckon the elegant and highly ornamented Dudley fossils, En- 
Fossils (64). Upper Silurian Crustacea. 
1. Lichas Anglicus, Bey- 
rich ; and its hypostome or 
labrum. 2. Calymene tu- 
berculosa, Salter ; also with 
its labrum. 3. Lichas Bar- 
randii, Fletcher. 4. Bey- 
richia Kloedeni, M'Coy ; na- 
tural size and magnified. 
The other figures are reduced 
to about half size. 
crinurus punctatus, Foss. 65. f. 5, and E. variolaris, f. 6. These, which are 
known by the name 1 strawberry-headed ' by collectors, are found on every slab 
of Wenlock limestone, but seldom perfect except at Dudley, whence the fine spe- 
cimens formerly in the cabinets of Mr. Gray and Mr. Fletcher were obtained. 
Cheirurus bimucronatus, Foss. 65. f. 4, figured from fragments only in Sil. 
Syst., is found perfect in the same collections, and in the cabinet of my friend 
the Rev. T. T. Lewis. The singular genus Acidaspis is now better understood 
than when I formerly described it ; and no less than six species of this genus, 
besides Acidaspis Brightii (PI. XVIII. f. 7, and Foss. 65. f. 8), are known in 
the Upper Silurian rocks. The head, Foss. 65. f. 9, of one of the largest species, 
called A. Barrandii by Mr. Fletcher, is here figured. It belongs to a group 
* Mem. Gcol. Surv. vol. ii. part 1. pi. 4. 
