578 DR MALCOLM LAURIE ON 



some distance, but finally gets itself lost in one of the black layers so common in this 

 bed, and the details of the posterior segments and the telson cannot be made out. The 

 tail segments appear to have been ornamented with longitudinal ridges possibly com- 

 posed of a series of knobs. 



The limbs are, as mentioned above, very imperfectly preserved. Careful following 

 out of what was left has however yielded some results. 



The chclicerse are well shown and are remarkable for the large size of the pincers 

 and the length of the basal portion. They project 4*5 mm. beyond the front of the 

 carapace and the movable limb of the pincers measures 3 mm. The inner border of the 

 fixed limb is crenulated, and probably the corresponding border of the movable limb was 

 also. Compared with Palceophonus nuncius, the basal part of this limb is longer, while 

 the width both of the basal part and the two limbs of the pincers is considerably less. 

 They seem to agree more closely with the Palceophonus from Lesmahagow (7)- 



The second pair of appendages — Chelae — are partially preserved on the left side — t he 

 right side showing only the barest traces of them. The segments agree in form with 

 recent Scorpions so far as their outline can be ascertained. The fourth segment is much 

 longer than in P. nuncius, and the hand seems to have been stouter. This last, how- 

 ever, is so badly preserved that it would be unwise to say anything definite about its 

 form. Part of one of the walking legs is preserved. The proximal part is very indis- 

 tinct, but the last three segments are visible. Unfortunately the extreme end is gone, 

 so it is impossible to say whether these limbs ended in a single spine as in the other 

 species of Palceophonus. 



This specimen is the fourth scorpion from Silurian strata. The other three are 

 Palceophonus nuncius of Thorell (9) from Gothland ; a Palceophonus described by 

 Peach (7) from the collection of the late Dr Hunter, Selkirk ; and Proscorpius 

 osborni of Whitfield (11) from the Lower Helderberg rocks of America. This pre- 

 sent form is probably the oldest of the four, and this makes it the more to be regretted 

 that so few details can be made out. 



Sltmonia. 



Slimonia dubia, n. sp. PL I., figs. 2-3. 



Carapace quadrangular ; eyes at the anterior corners ; body tapering gradually ; 

 telson oval, terminating in a long sharp spine. 



The type of this species is a very badly preserved carapace (fig. 2), with parts of 

 the first eleven segments attached. Enough can, however, be made out to place it as 

 a Slimonia, as no other genus possesses the quadrangular carapace with eyes at the 

 corners. The other specimen I have relegated to this species shows the body segments 

 and telson of a somewhat larger individual than the type. The telson has a more 

 elongated form than in S. acuminata, and the broadest part is not so far back. The 



