1* TPJLOPJTEK OF GIRVAN 



2. Ampyx drummuckensis, sp. nov. Plate III, figs. 1 — 5. 



? 187G. Ampyx rostratus, Armstrong and Young, Cat. West. Scot. Foss., p. 15. 

 1879. Ampyx rostratus, Nicholson and Etlieridge, Mon. Silur. Foss. Girvan, fasc. ii, p. 178, pi. xii, 

 figs. 14, 15 ; pi. xiii, figs. 1 — 3. 



Specific Characters. — Head-shield triangular, acutely pointed in front, a little 

 longer than wide. Glabella long, diamond-shaped, expanding to middle, then 

 contracting to apex; greatest width across middle and equal to about half the length; 

 convex with greatest elevation at middle, thence tapering anteriorly ; a low keel more 

 or less obsolete runs along whole length of glabella, but bifurcates near front end 

 into narrow ridges enclosing groove which is continued along spine ; front end of 

 glabella conical, rounded, freely projecting in front of cheeks, and furnished with 

 long straight horizontal spine two to three times the length of the glabella and 

 marked with a broad shallow groove along its whole length. Base of glabella 

 truncated, not pointed, and about half the width of broadest part. Near the base 

 is a pair of transverse deep isolated pits or short grooves (seen only in some 

 specimens) a little in front of the occipital furroAV, which is faint and separates off a 

 feebly rounded projecting occipital segment. Axial furrows shallow lint distinct, 

 nearly straight, diverge anteriorly at about 30°, dying out almost completely 

 (except in casts) a little behind the middle of the glabella. At this point a pair of 

 oblique deep pits (only visible in casts) occurs on each side of the glabella. 



Fixed cheeks triangular, weakly convex, gently bent down, extend halfway up 

 glabella to broadest part, where they slope downwards rapidly. Neck segment 

 distinct, marked off by strong straight furrow. Facial suture weakly sigmoidal, 

 and its general course at about 75° to posterior margin. Fixed cheek at base 

 measures about one and a half times basal width of glabella. 



Free cheeks narrow, marginal, with genal angles furnished with long curved 

 flattened and grooved spines, at least half as long again as the head-shield. Surface 

 of shell coarsely punctate (seen also in casts). 



Thorax (imperfectly known) of five segments, short, broad, not as long as 

 head-shield. Axis convex, wider than pleura?, cylindrical. Pleuras horizontal, 

 straight, flattened, grooved along their length. 



Pygidium triangular, more than twice as wide as long with broad bevelled con- 

 centrically striated border. Axis conical, pointed, reaching bevelled border behind, 

 less than one-third the width of pygidium, gently convex, segmented along whole 

 length, furnished with 7 — 9 pairs of tubercles arranged in a row on each side of 

 axis and connected by narrow transverse furrows, thus indicating the segments. 

 One strong simple complete ring marked off at front end of axis. Axial furrows 

 strong. Lateral lobes weakly convex, smooth, with only one strong oblique furrow 

 near front edge. Surface of shell of pygidium coarsely punctate. 



