550 bulletin: museum of comparative zoology. 



Basal lobes completely separated from the body of the 

 glabella. 



Neek-furrow strongly convex forward icarus Billings 



Axial portion of neck -furrow only strongly convex forward 



pompilius Billings 



Ceraurinus marginatus, sp. nov. 

 Plate, fig. 1. 



This species is known from a single specimen, which, with the excep- 

 tion of the posterior segments of the thorax and the pygidium, is nearly 

 perfect. 



The cephalon is semicircular, of moderate convexity, and bounded 

 by a broad marginal border, which is one of the most distinguishing 

 features of this species. The glabella is subrectangular, rounded in 

 front, and is slightly convex. The glabellar furrows are sharply 

 and deeply incised and are about one third +he width of the glabella 

 in length. They are almost at right angles to the parallel sides of the 

 glabella, but slope very slightly backward. The posterior three gla- 

 bellar lobes are about of a size. The frontal lobe is slightly larger. 

 The constriction connecting the inner ends of the posterior pair of 

 glabellar furrows with the neck-furrow is extremely faint. The gla- 

 bella is smooth. The cheeks are large, triangular, slightly convex, 

 and faintly pitted. The eye is in the middle of the cheek, opposite 

 the second glabellar furrow, and is moderately large and Asaphus-like. 

 The faceted surface slopes outward instead of being vertical as in 

 most of the Cheiruridae. The palpebral lobe is large and triangular 

 with a linear depression on its upper surface. A strong eye-line runs 

 from the base of the palpebral lobe to the base of the first pair of 

 glabellar furrows. The facial suture, running forward from the 

 tip of the palpebral lobe, bends inward and cuts the anterior margin 

 in front of the glabella. From the tip of the palpebral lobe, the pos- 

 terior portion of the facial suture at first curves backward and then 

 curves outward, convex to the anterior, till just across the lateral 

 furrow. It then slants diagonally across the border and cuts the mar- 

 gin just in front of the genal angle. 



Thorax probably of eleven segments. The type is imperfectly 

 preserved after the tenth thoracic segment. The axial lobe is convex, 

 about one fourth the width of the thorax in width and tapers gently 



