H, Woodward—Descriptions of New Paleozoic Crustacea. 199 
This spine is so peculiar in its form, and so distinct from any 
other specimen as yet met with, that I have ventured to name 
it Stylonurus ensiformis. ‘The specimen is in the 
collection of Mr. James Powrie, F.G.S., of Res- 
wallie. 
3. PTERYGOTUS MINOR. Sp. nov. Pl. X. fig. 2. 
Associated with the great Pterygotus anglicus, |||| 
in the Old Red Sandstone of Farnell in Forfar- || # 
shire, Mr. Powrie has discovered the smallest 
Pteryg otus known. 
The specimen is only 2} inches in length, by 2 of 
an inch in breadth. 
It is evidently a new species, as it presents a re- 
markable difference from all other forms of this genus. 
The eyes are within the margin; whilst in other 
species they are placed upon the latero-anterior angles. 
The position of the eyes has been considered by some 
palzontologists to be of generic importance; but I am 
inclined to believe it only of specific value; for in 
the larval stages the eyes do not occupy the same 
position as in the adult animal. 
The specimen is entire, and exhibits the relative 
proportions of the head, thorax, and abdomen, as 
well as the telson or tail-joint, with its strong 
median ridge flattened down upon the surface of the 
shale. The swimming-feet can also be seen in site. 
Dimensions of Pterygotus minor.—Greatest length 
of carapace, 4 lines, width 6 lines; space between the 
eyes 2 lines. 
lst segment (thoracic=I1st to 6th), 1 line long, 6 
lines mide: 2nd, 2 lines long, and 7 wide; 3rd, 4th , Syfonmusensiformis, 
and Sth, 13 ines long, and 8 dines wide ; 6th, 12 lines are Gla eae 
long, and 7 lines wide; Bae seement (abdominal Sandstone foray, 
=7th to 12th), 1? lines long, and 6 lines wide; 8th, 
13 lines long, and "5 lines wide; 9th, 1? lines long, and 4i wide; 10th, 
2 ‘lines long, by 4 lines wide; 11th, 2 ‘lines long, and 8b wide; 12th, 
3 lines long, and 3 wide; telson, or tail-plate, 7 lines long, and 
2 lines wide. Total length of swimming-foot, 6 lines. 
The impress of the specimen is so exceedingly delicate, that it pre- 
sents rather the appearance of a ‘ghost’ than of an actual reality, 
and requires to be held obliquely in a good light in order to make 
out even these details clearly. The eyes are the only parts slightly 
elevated above the surface of the shale. 
The specimen which is here described is unique, and was 
obtained from the indurated shale overlying the ‘Arbroath 
Paving-stone,’ and from which Mr. Powrie has obtained so many 
new and interesting species of Fishes. ‘The shale is very finely 
laminated, and breaks up throughout into cuboidal fragments. 
