LOWEE OLD EED SANDSTONE. 
447 
¥i<r. 504. 
wing-like form and feath¬ 
er-like ornament of the 
thoracic appendage, the 
part most usually met 
with. Agassiz, having 
previously referred some 
of these fragments to the 
class of fishes, was the first 
to recognize their crus¬ 
tacean character, and, al- 
thouo'h at the time unable 
o ^ 
correctly to determine the 
true relation of the several 
parts, he figured the por¬ 
tions on which he founded 
his opinion, in the first 
plate of his “ Poissons 
Fossiles du Vieux Gres 
Rouge.” 
A restoration in correct 
proportion to the size of 
the fragments of JP. angli- 
cus (Fig. 504), from the 
Lower Old Red Sandstone 
of Perthshire and Forfar¬ 
shire, would give us a crea¬ 
ture measuring from five 
to six feet in length, and 
more than one foot across. 
The largest crustaceans 
living at the present day 
are ihelnachus Kmmpferi^ 
of De Haan, from Japan (a 
brachyurous or short-tailed crab), chiefly remarkable for the 
extraordinary length of its limbs; the fore-arm measuring four 
feet in length, and the others in proportion, so that it covers 
about 25 square feet of ground; and i\\e Limulus Molucca- 
nus^ the great King Crab of China and the Eastern seas, which, 
when adult, measures 1-J- foot across its carapace, and is three 
feet in length. 
Besides some species of Pterygotus^ several of the allied 
genus PJurypterus occur in the Lower Old Red Sandstone, 
and with them the remains of grass-like plants so abundant 
in Forfarshire and Kincardineshire as to be useful to the 
geologist by enabling him to identify the inferior strata at 
distant points. Some botanists have suggested that these 
Pterygotus anglicus, Agasp. Forfarshire. Ven¬ 
tral aspect. Kestorecl by H. Woodward, 
F.G.S. 
a. Carapace,^ showing the large sessile eyes at 
the anterior angles, b. The 'inetastoma or 
post-oral plate (serving the office of a lower 
lip), c, c. Chelate appendages {antenmdes). 
d. First pair of simple palpi {antennce). e. 
Second pair of simple palpi {mmidibles). /. 
Third pair of simple palpi (first maxillce). 
g. Pair of swimming feet with their broad 
basal joints, whose serrated edges serve the 
office of maxillce. h. Thoracic plate covering 
the first two thoracic segments, which are 
indicated by the figures 1, 2, and a dotted 
line. 1-6. Thoracic segments. T-12. Ab¬ 
dominal segments. 13. Telson, or tail-plate. 
