LIFE-FORMS OF THE PAST AND PRESENT. 
393 
into Silurian times ; * * * § or, like the Isopoda, may reach back to the 
Devonian epoch.f The Cirripedia, a most aberrant group of 
Crustacea (represented abundantly in the seas of to-day by the 
pedunculated Lepas (“Ship Barnacle”) and the sessile Balanus 
(or “ Acorn Shell ”), so common on the bottoms of ships which 
have been long at sea, and upon the piles of piers, and on sea- 
walls, and rocks washed by the tide), carry back their history, 
the latter through the Tertiary rocks to the Upper Chalk , i the 
former to the earliest Secondary rocks, whilst a single form is 
found in the Wenlock shale of Dudley (Upper Silurian). § 
The King-Crabs, next to the Entomostraca, undoubtedly 
enjoy the most extended range in time ; occurring in consider- 
able numbers in the Lithographic stone of Solenhofen, with 
characters scarcely, if at all, differing from those species now 
found living on the east coast of North America and in the 
seas of China and Japan. About seven species occur in the 
Coal-measures (See Plate XC., figs. 6, 7, 8,), and one actually 
in the Silurian (See Plate XC., fig. 9) of Lesmahagow in 
Lanarkshire ; || these palseozoic forms closely resemble the larval 
stages of the living Limulus (See Plate XCI., figs. 21-24). 
The accompanying Table will best exhibit the successive 
appearance of the chief orders of Crustacea, and beside them 
are placed the Arachnida, the Myriapoda, and the Insecta, with 
their representatives in palaeozoic strata ; thus giving the range 
of the entire sub-kingdom of the Arthropoda in time. 
But omitting the solitary instances, already referred to, of 
those higher forms which have left traces of their existence in 
palaeozoic times, it is evident that, from the Carboniferous strata 
downwards, we have to deal for the most part with three 
great groups of Crustacea, namely the Merostomata, the Trilo- 
bita, and the Entomostraca. 
The first of these, the Merostomata (or thigh-mouthed 
* I believe the form I have described under the generic name of Necro- 
gammarus, from the Lower Ludlow, to; be an Amphiphod. See u Trans, 
Woolhope Club, Hereford,” 1870, p. 271.’ 
t I have described a part of a giant Crustacean, which I believe to be an 
Isopod, under the name of Prcearcturus gigas, from the Devonian of Here- 
fordshire. See “Trans. Woolhope Club, Hereford,” 1870, p. 266. 
X Pyrgoma cretacea, H. Woodward, “ Geol. Mag.,” 1868, Vol. V. p. 258, 
pi. xiv. figs. 1, 2, 3. From the Upper Chalk near Norwich is at present the 
oldest. 
§ Turrilepas Wrightn, H. Woodward, " Quart. Journ. Geol. Soc.,” 1865, 
Yol. XXI. p. 486, pi. xiv. figs. 1-6. 
0 Neolimulus falcatus , H. Woodward, “ Geol. Mag.,” 1868, Yol. V. p. 1, 
pi. i. fig. 1. 
