12 THORELL & LINDSTRÖM, SILURIAN SCORPION FROM GOTLAND. 



thorax. It is broader than long, at least in the second and third pairs of legs (in the 

 other pairs it is in part concealed), becoining gradually a little longer in proportion 

 to its breadth in the posterior pairs. It appears to have been cylindrical, with the 

 distal end somewhat obliquely truncated. 



The next joint or thigh (feraur) (/) resembles the trochanter; it is if anything, 

 slightly narrower and longer, and towards the distal end, the sides are slightly round- 

 ed and somewhat tumid. In the first pair of legs it is much broader than long, 

 whilst in the fourth pair the length and breadth are equal. The fourth joint or tihia 

 (tb) is similar in form to the third or femur, but it is more slender, and distinctly 

 longer. It is not compressed, nor is the antero-inferior margin longitudinally rounded, 

 as in recent scorpions. In the first pair of legs, the length and breadth of this joint 

 are equal; in the fourth pair it is about one-fourth longer than broad. The fifth 

 joint {first joint of tarsus) (f^) is distinctly more slender than the tibia and only about 

 half its length: it is somewhat broader than long, and tapers very slightly and gradually 

 from the base to the tip. It is armed with a strong, pointed, nearly straight spine about 

 as long as the joint itself, nearly parallel to its axis, and which issues from the 

 antero-inferior part of the margin of its distal end. The sixth joint {second joint 

 of tarsus) {t^), is considerably longer as well as narrower, than the fifth joint; it is 

 about double the length of the tibia. It is approximately cylindrical, and the distal 

 extremity is furnished with from one to three minute, triangulär scale-like bodies. 

 The seventh or last joint {third tarsal) {t^) is about the same length as the sixth, but 

 a little more slender at the base than that joint; it tapers gradually to the pointed 

 tip, forming a long, robust, slightly curved, claw or spike^). 



As the dorsal surface of the specimen is exposed, the inferior side of its cepha- 

 lothorax, with the bases of the palpi and the legs, and the sternal plate, are concealed 

 by the matrix, as well as the ventral side of the two first abdominal segments with 

 the genital plate (operculum) and the combs^). But little can be seen of the ventral 



^) The legs appear to have been direoted, when the animal walked, much in the same way as in our recent 

 scorpions; but instead of being bent twice forwards, viz., between the thigh and the tibia, and between 

 the tibia and the first tarsal joint, the legs of our soorpion would seem to have been bent either forwards 

 between the trochanter and the thigh, or (1st pair) between the thigh and the tibia. 



-) In the Scotch Palreophonus found by Dr Huxter the ventral side is uppermost, so that the characters 

 of the ventral surface, which in our specimen are hidden by the matrix, can be distinguished. As these 

 probably differ but little from those of P. nimcius, we take the liberty of giving Mr Peach's preliminary 

 description of them. »The arrangement of the sternum shows a large pentagonal plate (metasternite), 

 against which the wedge-shaped coxa3 of the fourth pair of walking-limbs abut. The coxse of the 

 third pair bound the pentagonal plate along its npper margins, and meet in the mid-line of the body, 

 where they are firmly united. The coxfe of the first two pairs, as well as the bases of the palpi, are 

 drawu aside from the ceutre line of the body, showing that, as in recent scorpions, these alone were con- 

 cerned in manducation, or rather the squeezing out of the juioes of the prey. ]^'rom 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 chelicerse. Behind the pentagonal plate 

 and the ooxfe 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 . . . At the interiör angle of the inverted V 

 there hängs downwards a narrow bifid operculum flanked on each side by the combs, which have each 

 a broad triangulär rachis set along its lower edge with the usual tooth-like filaments. The combs al- 

 most hide the first of the four ventral sclerites, which bear the breathiug-apparatus in recent scorpions, 

 notwithstanding which all four of these exhibit on tlieir right side undoubted slit-like stigmata at the usual 

 places». (Peach, Ancient Air-breathers, in »Nature», Vol. 31, M 796, p. 297 — Jan. 29, 1885), 



