﻿32 MR. E. S. C0BB0LD OX TRILOBITES FROM [Feb. I9IO r 



sx^ine ; three pairs of furrows directed strongly backwards are some- 

 times visible at the sides, but they are frequently almost obsolete. 



O.ccipital furrow. — Sometimes traceable all across, some- 

 times only represented by impressions at the sides. 



Occipital ring. — Merged into the base of a very strong nuchal 

 spine, which projects backwards over several thoracic segments. 



Axial furrow. — The change in vertical curvature all round 

 the glabella indicates its limits very definitely, but there is no im- 

 pressed line or hollow. 



Fixed cheek. — Subquadrangular ; as wide as the glabella; 

 almost horizontal for about half its width, rising a little in the 

 third quarter, and falling steeply to a hollow or groove, the outer 

 margin of which rises to form the eye-lobe ; posteriorly the surface 

 of the cheek falls steeply to the postero-lateral groove ; anteriorly 

 it slopes gently and evenly down to the frontal limb, extending 

 a very little beyond the ocular ridge. 



Eye-lobe. — A little less than a third of the length of the head- 

 shield (without the spine) ; rather nearer to the posterior than to 

 the anterior margin ; elevated at its interior end above the ocular 

 ridge, and having its upper surface distinctly inclined backwards 

 as seen from the side. 



Ocular ridge. — Almost obliterated at its commencement near 

 the glabella, but gaining in definiteness, by reason of the slight 

 depression behind it, as it crosses the front slope of the cheek 

 towards the eye-lobe. 



Frontal limb. — Extending for a quarter of the length of the 

 head-shield in front of the glabella ; composed of a deep and wide 

 rounded hollow and a very convex marginal rim : the hollow and 

 rim lose intensity to right and left, and are hardly discernible at 

 the line of the facial suture. 



Postero-lateral limb. — Consisting of a groove widening con- 

 siderably towards the facial suture, and a well-marked but rather 

 narrow raised rim. At a distance from the glabella equal to the 

 width of its base there is a strong geniculation, sometimes rising 

 so much that it might be called a tubercle; beyond this the sur- 

 face of the limb slopes down steeply to the facial suture, and the 

 groove and raised rim gradually fade away. 



Facial suture. — Not well seen from above, owing to the 

 curving over of the sides of the cranidium ; the anterior branch is 

 short, subparallel to the axial line of the shield, and curves very 

 slightly outwards ; the posterior branch is somewhat sigmoidal, but 

 also short, and meets the posterior border behind the eye-lobe. 



Test. — The test in this species seems very thick and strong, and 

 all the minor features, such as the glabellar grooves, or ocular 

 ridge, are softened or almost obliterated from this cause. I have 

 not seen any internal casts. The actual surface is smooth, but not 

 polished, and under a strong magnifier appears to be of extremely 

 fine grain. 



As a rule, no surface-marks arc visible on the upper surface ; 

 but on one nuchal spine attached t© a glabella [158] there are 



