October, 1913. New Trilobites — Slocom 55 



leading up to longitudinally elongate depressions situated just in front 

 of a line joining the anterior edges of the eyes and somewhat nearer to 

 the eyes than to the median line of the cephalon. These depressions 

 appear as sublunate grooves on the casts, but on the surface of the test 

 only as a slight flattening. The regular curvature of the cephalon, 

 aside from the flattening just referred to, is interrupted only by the 

 palpebral lobes. Eyes far apart, situated at about half their length 

 from the posterior margin of the cephalon. Facial sutures originate on 

 the posterior margin of the cephalon on a level with the lower edges of 

 the eyes, from whence they pass forward and upward around the eyes, 

 thence obliquely downward to the antero-lateral margin of the ceph- 

 alon. Free cheeks small, genal angles obtusely rounded. Occipital 

 ring not discernible on either test or cast. 



Thorax composed of ten segments, smooth and flat, gradually 

 narrowing to the almost obsolete dorsal furrows, at which points they 

 bend backward and downward to the lateral margins ; the axis occupies 

 about two-thirds of the width of the thorax; dorsal furrows appear on 

 the casts as two parallel grooves. 



Pygidium strongly arched, transversely oval, length about two- 

 thirds the width, no trace of the dorsal furrows. 



Five specimens were used by the writer in making this description. 

 The holotype (PL XIV, fig. 1) is an enrolled specimen having a portion 

 of the front of the cranidium missing. It is in the private collection of 

 Mr. A. G. Becker. A paratype (PI. XIV, figs. 2-3) consists of a com- 

 plete cephalon attached to nine complete thoracic segments and a 

 portion of the tenth. This specimen was collected by Prof. Calvin and 

 is a part of the geological collection of the State University of Iowa. 

 The other paratype (PI. XIV, fig. 4) is a pygidium attached to the 

 seven posterior thoracic segments. It belongs to the Museum collec- 

 tions (Mus. No. P 16708). Two somewhat distorted natural casts 

 (Mus. No. P 16854) were also used in making this description. These 

 casts were presented to the Museum by Mr. Becker. The dimensions 

 of the type specimens are as follows: Holotype: Cephalon 18 mm. long, 

 31.5 wide; pygidium 15 mm. long, 26.4 mm. wide; distance around the 

 coiled specimen 74.5 mm. Allowing for the convexity of the cephalon 

 and pygidium would make the length if unrolled about 60 mm. Speci- 

 men from the State University of Iowa: Cephalon 19.6 mm. long, 

 32.3 mm. wide and 18 mm. thick. Specimen P 16708: Pygidium 11 

 mm. long, 19 mm. wide, length of pygidium and the seven posterior 

 segments of the thorax 33 mm. 



Remarks. — Specimens of this species have been referred to B. 

 orbicaudatus Billings by Calvin, Savage, and others in the various Iowa 



