3S 



ME. 70. S. COIilSOLD OX THE TEILOBITE FATJKA [Marcll I9I3. 



Ptychoparia Corda. 



Subgenus Liostracus Angelin. 



Ptychoparia (Liostracus) lata, sp. nov. (PI. II, figs. 10 rt-17 c.) 



Ptychoparia (Liostracus) , sp. allied to Ft. (L.) puleliella Cobbold, Hep. 

 Brit. Assoc. 1912 (Dundee). 



Of the seven or eight easts of cranidia in the collection from the 

 Breccia-Bed the internal cast [1403] is selected as the type for 

 the species. It is the only one that seems to retain the natural 

 convexity without distortion. 



Craxidium : General form. — Trapezoidal, with front well 

 rounded, so as to be a segment of a circle ; features in strong 

 relief. 



Size. — Length, exclusive of occipital spine, =8 mm.; width 

 across eye-lobe = 10 millimetres. 



General convexity. — Considerable ; ratio, about 1 : 3*2. 



Glabella. — Convex and wide ; tapering slightly forwards ; apex 

 bluntly rounded ; bent down strongly forwards ; highest in th» 

 posterior third of the length ; widest at the base, where it is very 

 little less than the length ; two pairs of the lateral furrows are 

 just discernible on the internal cast. 



Occipital furrow. — Wide and well-marked; a little shallower 

 in the middle than at the sides. 



Occipital ring. — Almost entirely merged in the base of a 

 strong, but rather short, spine, which projects upwards to a height 

 distinctly greater than that of the glabella, and backwards to a 

 distance from the occipital furrow a little more than half the 

 length of the glabella. 



Axial furrow. — Continuous round the sides and apex of the 

 glabella ; wide and well-marked, but not deep, except when the 

 head-shield has been compressed vertically. 



Fixed cheeks. — Scarcely half the width of the glabella ; gently 

 convex in the middle ; descending steeply to the eye-lobe and 

 towards the postero-lateral furrow, but more gently forwards ; 

 continuous by a narrow convex space round the apex of the 

 glabella ; highest opposite the posterior third of the glabella. 



Eye-lobe. — Convex and raised as compared with the slope of 

 the cheek, from which it is separated by a distinct groove ; situated 

 about half-way along the course of the facial suture, and having a 

 length approximately equal to half that of the glabella. 



Postero-lateral border. — A rather flat fold, widening a 

 little outwards ; separated from the fixed cheek by a wide and 

 shallow furrow, with 'which the occipital furrow makes one straight 

 line across the head-shield. 



Front.— Extending forwards for a distance nearly equal to half 

 the length of the glabella, and consisting of three sub-equal parts : 

 (1) a convex space, connecting the fixed cheeks ; (2) a shallow 

 hollow ; and (3) a convex marginal fold. 



