NO. 3 CAMBRIAN AND OZARKIAN TRILOBITES II5 



SYMPHYSURINA WOOSTERI Ulrich (MSS.) 



Plate 21, figs, i-ii 



Symphysurina woosteri Ulrich in Walcott, 1924, Smithsonian Misc. Coll., 

 Vol. 75, No. I, p. 37, fig. 8. (Illustrated but not described.) 



Quotation from Dr. Ulrich's manuscript : 



" Carapace of medium size, approximately three cm. in length and 

 two cm. in width. 



" Cranidium strongly convex, arching uniformly from front to 

 back, with a low median ridge, the outline expanding decidedly for- 

 ward from the eyes, the sutural edge here making a gently sigmoid 

 curve; anterior edge moderately accurate in both dorsal and front 

 views, distinctly rimmed by a marginal furrow: palpebral lobes of 

 medium size^ contracted behind, situated mostly behind the midlength, 

 convex in the inner part, then concave, and finally curving upward 

 to the edge : posterior liinbs small, narrowly tapering and declining 

 outward : neck ring narrow, obscurely defined in casts of the interior 

 and perhaps unrecognizable on the exterior: dorsal furrows moder- 

 ately deep near the posterior edge, quite obsolete in passing the palpe- 

 bral lobes, but reappearing faintly impressed in front of them, thus 

 obscurely separating the glabellar region from the anterior fixed 

 cheeks. 



" Free cheeks sub-triangular, terminating outwardly in a strong 

 compressed genal spine: inner area moderately convex, separated 

 by a narrow furrow from the outer border, which is narrow and 

 wire-like at the front, but widens and flattens rapidly in approaching 

 the genal angle, beyond which it becomes obsolete before reaching 

 the posterior edge : eye prominent, rising abruptly out of a flattened 

 or slightly concave area, the minutely ocellated band at the top com- 

 prising less than half of the rounded ocular elevation : anterior edge 

 thick, especially in the part that projects under the front of the 

 cranidium, the thinner lateral part with nine pits for the reception of 

 the ends of the thoracic segments. 



" Pygidium rounded sub-triangular, rather strongly convex, the 

 axis prominent, distinctly outlined by the dorsal furrows, extending 

 to the posterior edge where it tapers rapidly and is further produced 

 as a slender sharply pointed free spine : tip of spine rising to the 

 level of the axis and reaching a point one-fourth or less of the total 

 length of the pygidium behind its margin : pleural lobes convex in 

 the inner parts, thence sloping somewhat steeply, and commonly 

 through an obscurely developed marginal concavity, to the edge : 

 segmentation obsolete or very obscurely indicated excepting the first 



