CRUSTACEA. 69 



AC I DAS T 1 D.H. 



ACIDASPIS, Murchison. 1839. 



ACIDASP1S CALLICERA, 11. Sp. 



PLATE XVI ii, KIGS. 1-13. 



General Form and Outline. Body ovate; anterior margin slightly transverse; 

 lateral margins evenly converging from the base of the cephalon. 



Surface convex along the axis, depressed on the pleurae. Length to width 

 as 4 to 3. 



Cephalon transversely sub-rectangular, anterior and posterior margins sub- 

 parallel, lateral margins divergent at the genal angles. Width equal to 

 rather more than twice the length. 



Facial Sutures beginning on the posterior margin, just within the genal 

 angles, passing inward and forward over the eye-lobes, thence forward, con- 

 verging slightly to the frontal margin. 



Glabella sub-quadrate, frontal lobe elongate, convex, elevated, extending 

 from the frontal margin to the occipital furrow: sides parallel. Lateral lobes 

 in two pairs, pyriform, the posterior pair the larger, and both separated from 

 the frontal lobe by elevated furrows. The lateral lobes are included by a 

 ridge which extends from the anterior limb of the frontal lobe to the 

 eye and thence to the axial furrows. Occipital furrow narrow, becoming 

 rapidly obsolete upon the cheeks. Occipital ring broad, arched and bearing 

 a short central spine. 



Cheeks broad, slightly concave and sloping abruptly from the elevated eye- 

 Jobes. Border moderately thickened and produced at the genal angles into 

 long, slightly incurved, diverging spines; above this the margin is fringed 

 with short spines which are reduced to mere denticulations in front. 



