from Bolton, Lancashire. 397 



second somite may possibly be a portion of the first, or the first in some 

 displaced position ; it is seen much better on the piece of shale bearing 

 the impression than on the one bearing the fossil itself. Some hint as 

 to the shape of the first tergum is perhaps given by the pleural lamina? 

 of the second ; these extend forward beyond the second tergum and 

 their inner edges continue to diverge, as though to accommodate a first 

 tergum which carried still further the spreading form of the second. 



The succeeding somites, the second to the eighth, are well defined. 

 The second is nruch larger than the rest ; the third to the 

 seventh are nearly ecpual in length and show a regular decrease in 

 breadth ; the eighth is narrower and longer than any of the others. 

 The second tergum bears a pair of large but indistinct tubercles, and 

 there are traces of smaller and still less defined tubercles occurring in 

 pairs, one on each side, on the succeeding somites. A low, rounded 

 ridge runs down the centre of the terga, originating in the triangular 

 space between the tubercles on the second tergum. A rounded 

 swelling occupies the anterior part of the eighth somite, and may have 

 been present in life ; it fits in well with the converging lines formed 

 by the lateral edges of the preceding terga. Behind this swelling, and 

 a little to one side, there is an oval papilla, grooved in the middle, 

 which is possibly the imprint of a crushed anal plate lying below. 

 The integument is preserved over the greater part of the fossil, and is 

 everywhere finely granulated. It is missing, however, from the outer 

 parts of the pleural laminae (with the exception of the foremost lamina 

 on the right), and these show towards their outer edge a rather coarser 

 granulation and pitting. The original drawing of Maiocercus celticus 1 

 indicates a similar pitting on the underside of the laminae. The 

 concavity of the outer margins of the lamina? is not uniform. It is 

 well marked in those of the fifth, sixth, seventh, and eighth somites, 

 but not in those of the second, third, and fourth. In the case of these 

 three anterior lamina?, however, I am inclined to attribute the shape 

 of the margin to distortion. The whole front of the opisthosoma is 

 bent somewhat backwards on the left side, and the edges of the 

 anterior laminae on that side are notched here and there in a way that 

 suggests crumpling. In the restored outline I have assumed that 

 these laminae, if straightened out, would show nearly as much con- 

 cavity of margin as those that succeed them. 



The length of the opisthosoma is about 15 mm. and its breadth about 

 the same. The opisthosoma of Maiocercus celticus appears to be of much 

 the same breadth as that of the Westhoughton specimen, 3 but its length 

 is only about 11*5 mm. This difference in general proportions 

 presumably indicates specific distinctness ; it is greater than can be 

 accounted for with any probability by variability or by conditions of 

 fossilization. Specific names have little value in such a case, but it 

 might cause more trouble to leave the fossil unnamed than to add one 



1 By F. T. Howard & T. H. Thomas, Trans. Cardiff Nat. Soc, vol. xxviii, 

 plate facing p. 53, 1896. 



2 I have estimated the dimensions of Maiocercus celticus from Messrs. Howard 

 and Thomas's figure (see last footnote), which they state to be six times the 

 natural size. The figure on p. 60 of Mr. Pocock's monograph must have been 

 described as of natural size by mistake. 



