2 



BRITISH FOSSILS. 



glabella not more prominent than the cheeks, and much narrower, con- 

 tracted in front, and separated by a deep furrow from the front margin : 

 it has three lobes on each side, the basal one large, the middle one 

 nearly spherical, the third minute ; the forehead lobe is small, the neck 

 lobe large and prominent. The neck furrow is continued nearly to the 

 posterior angles, which are rounded. Cheeks gibbous, often more ele- 

 vated than the glabella, bearing the small eyes on their most prominent 

 part. These are placed opposite the middle lobe of the glabella, and at 

 some distance from it. A strong deep furrow separates the cheeks 

 from the glabella, except opposite the eye, where a buttress is thrown 

 across from the cheek, touching the middle glabellar lobe. The wings are 

 strongly bent downwards, and even inwards on the under surface of the 

 head, and the anterior margin is much recurved, and produced into a 

 snout. On looking at the under view of the head, the margin appears 

 greatly bent, and in the angle so formed the curved rostral shield, half 

 as long as broad, is inserted ; beneath this is attached the hypostome, 

 which is squarish oblong with the terminal angles rounded, strongly con- 

 vex forwards, the convexity terminating in a compressed tubercle ; one. or 

 two concentric lines, as if of growth, mark the surface, which is also 

 scabrous, like the general crust of the body. The axis of the 13 body 

 rings is convex, but narrower than the pleurae, and constantly tubercular 

 on the sides. The pleurse are horizontal half way, and then strongly 

 decurved ; their ends rounded posteriorly, and bent forward. Fulcrum 

 distant from the axis, about, half way from it near the head, — at one- 

 third, or rather less, behind. Pleurse sharply furrowed, the forward or 

 fulcral half somewhat narrower than the posterior. Tail nearly semi- 

 circular, with the front angles truncated, evenly and gently convex, the 

 axis not prominent, the sides decurved strongly towards their edges. 

 Axis not percurrent, narrow, conical, with seven rings, and a terminal 

 boss. Lateral ribs flattened, separated by sharp, narrow furrows, start- 

 ing at a wide angle from the axis, and curved back on the sides, simple, 

 or but rarely marked by a central line near their ends, — not bifurcate, as 

 in C. Blumeiibachii. 



Junior. — The proportions of the axis to the sides and the struc- 

 ture of the pleurse are similar, but the glabella is more cylindrical, not 

 widened below ; the tail is proportionally smaller, has the axis wider 

 and more convex, with fewer ribs, and there are but four distinct ribs on 

 each side. Fig. 8* is the tail of a young animal magnified. 



Variations. — In some the axis is a little more prominent, in others a 

 greater or less depression of the glabella occurs, and apparently the 

 production forwards of the snout is not always in the same degree. 

 But these variations are within narrow limits, and our species never 

 seems to approach C. BlumenhacJiii in convexity, especially with regard 



