CRUSTACEA AND ARACHNIDA OF THE CARBONIFEROUS ROCKS. 525 
the thinner parts of the sternal plates it is still quite translucent and almost 
transparent. 
Suborder XYPHOSURA. 
Genus Prestwichia, Woodward, 1867. 
A portion of a thoraco-abdominal buckler of a small Limuloid was obtained 
by Mr. Macconocuiz from Larriston, Upper Liddesdale, some time ago. The 
recent excavations near Langholm have brought to light several specimens of a 
large species of the same genus Prestwitchia, which, however, are very badly 
preserved. 
Prestwichia alternata, nov. sp., Pl. XXVIII. fig. 10. 
Carapace unknown. Thoraco-abdominal buckler about 6 mm. long by 
7 mm. broad, irrespective of telson and side spines. Anterior or articular margin 
not preserved. ‘There is a central area divided off from the broad margins by 
two deep trenches which proceed from near the anterior part, and after de- 
scribing arcs of circles converge upon base of the telson. Side branches are 
given off from this trench inwards, but they only pass a short distance into 
the central area. All the sulci are merely infoldings of the test, and not arti- 
culations. The telson, which is broken off at a distance of °5 mm. from its 
insertion at the sulcus, where it is ‘5 mm. broad, appears to have been much 
longer. Six recurved spines are seen on one side, which pass from the sulcus 
through the border, and are then curved gently backwards. These are alternately 
longer and shorter, the former on measuring an average 7 mm. and the latter - 
only 3 mm. It it this character which distinguishes it from Prestwichia 
anthrax, which species it closely resembles. 
Locality.—Larriston Burn, Upper Liddesdale. 
Horizon.—Calciferous Sandstone Series. 
Prestwichia rotundata, Woodward, 1867. 
Limulus rotundatus, Prestwich, 1840, Trans. Geol. Soc., 2nd series, vol. 
pl. xli. 
Several specimens of a Limulus, which may be provisionally referred to the 
above species, have been obtained from the fossil locality on the Esk near 
Langholm. They are in a bad state of preservation, owing to their being 
fossilised in shale, so that the limbs and the gill plates are pressed up through 
the dorsal shield. In addition, the whole cuticle is usually so much infested 
with innumerable calculi that it is rendered granular. Owing to these causes 
