CRUSTACEA. 135 



Phakthonides VARICELLA, 11. sp. 



PLATE XXIV, FIGS. '.'0-31. 



Cephalox. Intra-sutural portion only observed. Outline sub-circular. Frontal 

 area broad, concave, strongly recurved at the margin. Margin slightl} 

 thickened by doublure, elevated, reaching or exceeding the height of the 



glabella. Palpebral lobes conspicuous. 



Facial Sutures normal. 



Glabella elongate-ovate or pyriform, bounded by a low sulcus; convex, 

 slightly flattened above. Basal lobes strong; baso-lateral furrows broad and 

 deep; antero-lateral impressions duplicate, very faint upon the crust but 

 apparent upon the lower surface. 



Thorax not observed. 



Ptgidium broad, the outline being the arc of a circle whose center is the middle 

 of the first annulation. 



Axis elevated, relatively narrow and longitudinally arched, abruptly ter- 

 minating before reaching the posterior border; composed of eleven or twelve 

 transverse annulations. 



Pleura broad, depressed-convex, flattened at the margin, which is strongl} 

 thickened bv doublure. Pleural annulations eight, six of which are silicate 

 and double. The cast of the lower surface, which serves the purposes of 

 description, shows the last two annulations more distinctly than they would 

 probably appear upon the upper surface of the test. 



Surface of the cephalon ornamented by tubercles, which are scattered over 

 the glabella, and are stronger upon the adjoining frontal and lateral areas. 

 Upon the recurved marginal area the ornamentation changes to strong, abun- 

 dant punctae, which become finer toward the margin itself. On casts of the 

 lower surface this punctate structure is to a large degree lost. The pygidium 

 bears an axial row of bead-like tubercles with two less conspicuous rows on 

 each side. The pleura? show traces of three or four rows of tubercles, which 

 become obsolete toward the posterior extremity. 



