14 THORELL & LINDSTRÖM, SILURIAN SCORPION FROM GOTLAND. 



right of the second and third segments, which no doubt is the right end of the ven- 

 tral plate of the third segment, though it has been pushed much forward: this piéce, 

 which is seen mostly from the inner side, exhibits a very distinct slit-like, transverse, 

 slightly oblique stigma or sinraculum (fig. 1, sp), of precisely the same form and in the 

 same position as in recent scorpions (fig. 13). On the left side of the third dorsal 

 segment, a ventral plate protrudes, the interiör side of which is visible, and is proba- 

 bly to be regarded as a part of the fourth plate. 



As the hinder portion of the abdomen is also turned a little to the right, a 

 small part of the ventral plates of its fifth and sixth segments (fig. 2, Fj, Fg) are 

 visible to the left of the corresponding dorsal plates {D^, D^). The fifth segment of 

 the abdomen is almost rectangular, and nearly two and two-third times as broad as 

 long; its dorsal plate is slightly more than double as broad as long, with at least the 

 posterior angles rounded. The sixth segment is somewhat longer, but scarcely narrower 

 than the fifth: its dorsal plate appears to have been of the same form as that in front, 

 only a little narrower. Both these dorsal plates seem to have been a little granu- 

 lated. The impression of the seventh segment of the abdomen is somewhat longer and 

 narrower than the two preceding segments; it narrows backwards, and its sides are 

 rounded. It is at least half as broad again in front as behind, and somewhat shorter 

 than broad behind. It shows traces of three or four longitudinal impressed lines, which 

 probably correspond to four ridges or keels on the ventral plate of the segment. 



The tail (postabdomen) is long and robust, being about three and one-sixth times 

 the length of the cephalothorax. Its breadth at the base would seem to equal half 

 the breadth of the cephalothorax. It tapers but very slightly and gradually from the 

 base to the last segment (the poison vesicle), wdiich is not inconsiderably narrower 

 than the rest of the tail. Only the four hindmost segments are preserved with their 

 integument, and they are seen obliquely from below and from the left side. Of the 

 two first segments, only the impression of the ventral side is preserved. 



The first to the fifth segments were probably nearly cylindrical, and slightly 

 rounded along their sides. The impression of the first segment is a little broader, 

 especially at the base, than that of the following ones. The impressions of the two 

 first segments are about as broad as they are long, and slightly shorter than the next 

 following segments; the third, fourth and fifth segments are nearly equal in length, and 

 distinctly longer than broad; the fifth is, however, appai-ently a little shorter than the 

 fourth, and less elongated than in recent scorpions. The fourth segment (and probably 

 also those preceding it) is provided with at least six longitudinal, rather coarsely 

 granulated keels, four on the under surface and one on each side, more upwards. 

 The fifth segment has only five such longitudinal keels, three below and one on either 

 side, more upwards; it is also granulated, though more irregularly, in the intervals be- 

 tween the keels of the under surface. — The sixth caudal segment, or the poison vesicle, 

 (fig. 2, v) is short, and differs much in form from the preceding ones, somewhat less, 

 however, than in recent scorpions; its longer axis appears to have nearly the same 

 direction as that of the next preceding segment, whereas in existing scorpions the 



