cephalo-thorax in the Scottish example are chelate, but the palpi are not quite so robust. The walking-limbs, though not so clumpy as in P. nuncius, also terminate in a single claw-like spike. The arrangement of the sternum shows a large pentagonal plate (metasternite), against which the wedge-shaped coxæ of the fourth pair of walking-limbs abut. The coxæ of the third pair bound the pentagonal plate along its upper margins, and meet in the mid-line of the body, where they are firmly united. The coxæ of the first two pairs, as well as the bases of the palpi, are drawn aside from the center line of the body, showing that, as in recent scorpions, these alone were concerned in manducation, or rather the squeezing out of the juices of the prey; from the circumstance of these being drawn aside, the medial eyes are seen pressed up through the cuticle of the gullet, and a fleshy labrum (camerostome) appears between the bases of the chilicerae.
"Behind the pentagonal plate and the coxæ of the hindmost limbs there succeeds a space shaped like an inverted V, where the test is thin and wrinkled in the line of the long axis of the body. It is just along this line that the trunk or abdomen most easily separates from the cephalo-thorax in recent scorpions, and it is at once apparent that the trunk in this case is as far separated from the cephalo-thorax as it can well be without being detached. Similar longitudinally wrinkled skin is seen to unite the dorsal and ventral scutes up the whole right side of the trunk. At the interior angle of the inverted V there hangs downward a narrow bifid operculum flanked on each side by the combs, which have each a broad triangular rachis set along its lower edge with the usual tooth-like filaments. The combs almost hide the first of the four ventral sclerites, which bear the breathing apparatus in recent scorpions, notwithstanding which all four of these exhibit on their right side undoubted slit-like stigmata at the usual places. The fifth ventral scute of the trunk suddenly contracts posteriorly, and to its narrow end is articulated a long tail of five joints and a poison-gland with a sting. These joints are all constructed on the same principle as those of recent scorpions, and, as the articular surfaces are more highly faceted on the dorsal than on the ventral aspect (a portion of the tail of the specimen lying sidewise allowing of these observations), there can be no doubt that the animal was in the habit of carrying the tail over the head (so to speak), and stinging in the same manner as its recent congeners." These characters are shown in the accompanying illustration (Fig. 2), which is on the same scale as that of the figure of the Swedish example (Fig. 1), viz., about twice the natural size.
The animal is supposed to have wandered to the sea-shore in search of food, and there been imbedded in marine strata. From the completeness of the remains, it is evident that it can not have been carried far out to sea; the rocks of the formation in which the fossil was
