STYLONURUS SCOTICUS. 127 



remarkable of all the Palaeozoic Crustacea. It was found in an Old Red Sandstone 

 quarry in Montroman Muir, near the Forfar and Montrose Pike, by James Powrie, Esq., 

 of Reswallie. 



It is represented by a separate carapace (PI. XXII), the relievo side of which is in 

 Lady Kinnaird's cabinet, and the intaglio in the British Museum collection, and by an 

 almost entire example (PI. XXIII) which Mr. Powrie has been so fortunate as to obtain, 

 and which is preserved in his museum at Reswallie. The latter is lying on a slab of Old 

 Red Sandstone, at full length, with its dorsal aspect exposed, and the last five body- 

 segments detached entire, so as to show both the ventral and the dorsal surfaces. The 

 impression of the upper surface of the same on a separate slab exhibits in the most perfect 

 manner the epimeral portions of each of the last four segments, and also the remarkable 

 spatulate telson, 9 inches in length. 



The entire specimen is 3 feet 4 inches in length. The margin of the carapace is much 

 injured, but fortunately the separate carapace is well-nigh perfect, so that Ave are at no 

 loss to ascertain its contour. The posterior margin of the head is at its narrowest point 

 9^ inches in breadth and (about) 8 inches in length. 



There is an oblong median ridge in the centre of the carapace, terminating in a 

 smooth rounded prominence 3 inches from the posterior margin, and extending forward 

 about 2 inches. On either side of this central line are two smaller oblong prominences, rising 

 more in advance of the central ridge (4|- inches from the posterior margin, and about 

 fths of an inch in length), broader in front than behind, and curving away from the 

 median line, from which they are distant \ an inch on the other side. The central ridge 

 and lateral prominences are carried forward in a V-shaped elevation, which spreads out 

 laterally as it advances, the whole of the front and antero-lateral portion being coarsely 

 tuberculated, a single irregular row running down the median ridge. 



Tlie Eyes are situated parallel to the median ridge, and take their rise exactly 1 inch 

 on either side. They are almost identical in form with those of Phacops and Asaphus 

 among the Trilobites, being arranged in a semilunar or horseshoe shape around a raised 

 prominence. The cornea of the eye measures 22 lines, and is disposed outwards and 

 forwards, the centre being directed towards the latero-anterior angles. The eyes are 

 elevated about 5 lines above the surface of the carapace ; probably they may have been 

 even higher, but are somewhat compressed. 



Very minute scale-like markings are seen on the lateral and posterior margins of the 

 carapace and body-segments. 



The margin of the head is double around the frontal and latero-anterior portion, as in 

 S. Powriei and 8. Logani, &c. 



Thoracic Segments. — The first segment is lyg- of an inch in length and 10 inches in 

 breadth ; the lateral portion is rounded and curved upwards ; the surface is minutely 

 scale-marked. 



The second segment is 17 lines in length and 10 inches in breadth. A series of 



