﻿28 ME. E. S. COBBOLD ON TRILOBITES PEOM [Feb. I9IO, 



always raised above the depressed side of the cheek, rises distinctly 

 to the forward end, where it drops away abruptly to the place of the 

 ocular ridge. 



Ocular ridge. — Arising from the outer side of the axial furrow 

 n little in advance of the point where the side of the glabella begins 

 to curve round to the apex ; very slightly elevated, and sometimes 

 •only marked by a slight hollow or furrow behind it which connects 

 with the hollow in rear of the eye-lobe. 



Postero -lateral limb. — A triangular area, consisting of a 

 hollow which widens outwards, and a slightly raised margin which 

 is strongly geniculated just within the distance outward of the eye- 

 lobe, the geniculation being almost a tubercle. Beyond this point 

 the surface of the limb falls rapidly down to the facial suture. 



Frontal limb. — -Narrow, not more than an eighth of the length 

 of the head ; subequally divided into a flat area (or a shallow hollow) 

 and a slightly convex marginal rim ; both these features can be 

 followed in one of the specimens to right and left as far as 

 the facial suture. 



Facial suture.- — Anterior branch nearly straight forwards and 

 parallel with the axis of the head ; posterior branch a little curved 

 outwards, and extending as far out as the extreme limit of the eye- 

 lobe. 



Test. — Apparently thick and strong, sometimes almost polished 

 on the surface of the glabella ; having a finely granular aspect on 

 the rixed cheeks, and a few short raised lines on the front margin. 



Two detached pleurae occur on the same little piece of rock with 

 the cranidium [413]. These are smooth, widely furrowed, and 

 •strongly geniculated, but the ends are not visible. I cannot with 

 confidence assign them to this species, because at least two other 

 trilobites are represented by fragments on the same little block of 

 limestone. 



This form of the species seems to me to be intermediate between 

 Micmacca and Ellipsocephalus. From the type species of the former 

 it differs in the somewhat extended frontal limb, and in the rather 

 wider postero-lateral limb with the consequent lengthening of the 

 posterior branch of the facial suture. From the latter genus it differs 

 in the fact that the glabella is not expanded in front, nor is it 

 pentagonal in outline, nor is the frontal limb strongly bent down- 

 wards in front. 



The species seems nearest to Micmacca recurva, Matthew, but the 

 •eye-lobe of that species, as represented in his figure, extends farther 

 back, the postero-lateral limb is narrower, and the ocular ridge 

 seems to be differently developed; there is no 'obscure tubercle' on 

 the side of the glabella in the Comley form, which also is smaller. 



Micmacca ellipsocephaloides, var. spinosa. (PI. VIII, fig. 5.) 



Specimens [414 & J 12900] show the tubercle on the occipital 

 ring developed into a short spine directed backwards ; the axial 

 furrow is more distinctly hollowed, and traceable almost to the apex 



