542 Br. W. T. Caiman — On Arthropleura Moyseyi, n.sjJ. 



About the middle of the fossil the terga of eleven successive 

 somites are visible in their natural connexions. They are transversely 

 elongated plates of nearly uniform size, measuring about 2-5 x 8 mm. 

 where fully exposed, and slightly convex from side to side. Each is 

 crossed by two transverse tuberculated ridges, or rather, perhaps, 

 rows of partly confluent tubercles. The number of tubercles in each 

 row appears to be seven, but the surface has been much damaged 

 and the exact arrangement is hard to decipher. On each side the 

 terga are separated from the pleura by a well-marked groove, at the 

 bottom of which a suture or line of articulation is visible in places. 



The pleura are well preserved only on the left side of the body, 

 where twelve (perhaps thirteen) of them can be made out. Each is 

 a sickle-shaped plate, curving backwards to an acute point and 

 measuring about 65 mm. from the point to the articulation with the 

 tergum. Anteriorly, the pleura are slightly inclined forwards, but 

 passing backwards along the series they come to lie transversely to 

 the axis of the body. At or near the anterior edge of each is a strong 

 curved ridge defined by a deep groove, behind which the surface 

 becomes gently convex and bears a row of four or more prominent 

 tubercles. Indications of a second row of smaller tubercles are seen 

 on some of the pleura, but in every case the hinder edge is broken by 

 being crushed down on the ridge of the succeeding pleuron. 



The anterior portion of the fossil is obscure. Separated from the 

 foremost tergum by a space corresponding to perhaps two somites, 

 is a slightly convex oval area, marked off behind by a double 

 transverse ridge. This area, no doubt, represents the head of the 

 animal, but no further information can be obtained as to its structure 

 or appendages. 



Behind the series of somites described above, is a space of some 

 10 mm. in which no structure can be observed, although the pleuro- 

 tergal grooves seem to be faintly traceable across it. Behind the 

 gap the somites reappear, considerably smaller, and progressively 

 diminishing in size towards the hinder end. About ten of them can 

 be made out, and the pleural plates, which are visible on the right 

 side, become more backwardly directed as they proceed towards the 

 termination of the body, where some indication of a telsonic segment, 

 flanked by a pair of spines, can be faintly traced. In this posterior 

 part of the body the ornamentation is obscure, but tubercles similar 

 to those on the more anterior somites can be seen here and there on 

 the terga and pleura. 



The total length of the body, which is slightly curved to the right, 

 is about 60 mm., measured from the anterior margin of the head. 



Holotyfe. — Specimen No. 34, in the collection of Dr. L. Moysey, 

 JSTottingham. 



Horizon and Locality. — Coal-measures. " Yellow clays in the 

 neighbourhood of the Top Hard Coal, probably some 30 to 40 feet 

 below that seam. Shipley clay-pit, about 1^ miles north of Ilkeston, 

 Derbyshire." 



Remarks. — In the form of the pleural plates, their articulation with 

 the terga, the strong crescentic ridge on each, and the tubercles with 

 which they, as well as the terga, are ornamented, the fossil resembles 



