in the Coal- Measures of Belgium. 435 



segments are nearly the same in form, but tliey diminish insensibly 

 from the 2nd to the 6th segment. From 3^ mm. in breadth by l^ mm. 

 in length, they gradually decrease to 2 mm. in breadth and 1 mm. in 

 length. Each segment bears three punctee disposed symmetrically 

 near the centre and in close proximity to the posterior border, with 

 the exception of the 7th, or terminal, segment, which is ornamented 

 with a single small oval tubercle, situated on the median line and 

 near the anterior border. 



The 7th segment is three and a half times as long as the 6th, or 

 preceding, segment ; it spreads out in a fan-shaped form, being only 

 2 mm. broad at its anterior border, whilst it expands posteriorly to a 

 breadth of 6 mm. at its lower extremity. 



The lateral or epimeral border of the segments is about 3^ mm. in 

 breadth : its surface ornamentation has been preserved, and evidently 

 once extended over the central axis also, but has been removed from 

 this part of the specimen probably when separating it from its 

 counterpart. 



The divisions existing between each segment are clearly marked, 

 and are continued to the lateral border of the abdomen in the 

 form of a series of slightly raised lines, each marked by a row of 

 small tubercles. The outer border of each segment is slightly 

 concave or emarginated. 



A raised line, having its origin at the side of the central axis of 

 each abdominal segment, traverses the epimeral portion of the 2nd, 

 3rd, 4th, 5th, and 6th segments, forming a slightly sigmoidal curve, 

 inclining downwards and uniting with the posterior margin of each 

 segment near its border. 



Two lines, nearly parallel, and corresponding in contour with the 

 curvature of the exterior border of the abdomen, pass across the 

 lateral portion of each segment between the 1st and the 7th, when 

 they unite to form the limit of the central or axial part of the last 

 segment; by these lines the lateral border of the abdomen is divided 

 into three parts sloping fanwise towards the exterior. 



With the aid of a magnifying glass the surface of the border of the 

 abdomen is seen to be ornamented with fine granulations. 



From the general conformation of the segments, and after careful 

 comparison with numerous specimens, we are led to the conclusion 

 that the fossil under consideration represents the abdomen of a female 

 Brachyuran Decapod, and not the thoracico-abdominal segments of a 

 Limuloid Crustacean such as Bellinurus or PrestwicTiia, with the form 

 and segmentation of which it cannot be confounded. Nor are we 

 acquainted with any Arachnide which presents a form of abdomen 

 similar to this fossil. Nevertheless, in comparing this interesting 

 specimen with the abdomen of numerous modern short-tailed Deca- 

 pods, we cannot but observe that it presents many well-marked and 

 distinctive peculiarities, both in the form of the segments themselves 

 and also in their ornamentation. 



Having lately received from Mr. J. McMurtrie several fragments 

 of a new Crustacean discovered by him in the Eadstock Coal-field, 

 near Bristol, and also some other portions which I have reason to 



