526 B. N. PEACH ON FURTHER RESEARCHES AMONG THE 
the glabella, eyes, and nature of the thoraco-abdominal buckler are not 
apparent. The general form, however, is easily made out. There is an anterior 
buckler, the front margin of which describes a little more than a semicircle from 
25-40 mm. in radius, and ending at both sides in slightly recurved horns, so that 
the posterior margin is somewhat hollow, giving the appearance of a saddler’s 
knife. The breadth from tip to tip of horns varies from 2 to 3 inches. Within 
the semicircle are the arcs of two smaller circles, which intersect at the mid 
line anteriorly, and divide off a broad horseshoe-shaped plain margin, narrowest 
in front from a central area, the nature of which cannot be made out for the 
crushed limbs which are invariably confined within it. The thoraco-abdominal 
buckler is seen to be fringed with a similar serrated web as in the specimen 
figured by Woopwarp, In their size and proportions they differ slightly from 
the P. rotundata, though there are not sufficient characters displayed by the 
specimens to warrant their being made into a separate species. 
It is to be hoped that further examples may be obtained, which will throw 
some light on their character and anatomy. 
Locality.—River Esk, 4 miles south of Langholm. 
Horizon.—Calciferous Sandstone Series. 
Collector.—A. MACCONOCHIE. 
Genus Cyclus, de Koninck, 1841. 
A considerable number of specimens belonging to this genus have been 
secured during the operations at Langholm. They occur chiefly as flat discs 
or dome-shaped masses of radiating calculi, which have coalesced into a 
polygonal mosaic of calcareous plates. They vary from 3 mm. to 10 mm. in 
diameter. Several specimens are not so badly treated in this way, and in them 
the test is seen to be chitinous and flexible. Being embedded in shale, they are 
all more or less flattened, and apparently much in the same condition as the 
Cyclus Rankini described by Woopwarp as having been obtained from the 
Carboniferous Limestone of Carluke. They appear to belong to one species, 
which is different in some respects from any yet described. A few of the speci- 
mens exhibit the dorsal shield, which is plain and slightly embossed; while others 
only show the dorsal aspect of the borders, the rest of the upper surface being 
broken away, exposing the ventral or sternal arches, which radiate much as in 
the C. Rankini. Several large Limuloids and Eurypterids have been obtained 
from the same beds in which these occur, so that it is just possible they may be 
larva of the larger animals ; but, at the same time, it is quite as probable that 
they are themselves adult forms. From the fact that several of the Survey 
specimens exhibit limbs, the radiating lines of the sternum are most probably 
the divisions between the coxee, so that I am inclined to differ from Woopwarp, 
and to look upon the opposite end to what he does as being the anterior one. 
