132 G. P. MATTHEW : ILLUSTRATIONS OF 



eastern Newfoundland, and called attention to its divergence from the typical forms of 

 the genus, suggesting that Sfrenuella would be an appropriate designation for this aberrant 

 group of Agrauli, at the same time referring to the occurrence of a similar species in the 

 St. John Basin. In the species present here, however, there is not the same length of eye- 

 lobe, or short and direct posterior extension of the dorsal suture, but in these points in 

 which it varies from the Newfoundland species, it approaches the genera, Liostracus and 

 Ptychoparia. From the latter genus, however, it appears to be separated by the features 

 already mentioned in the preceding discriptiou of the genus Agraulos, as well as by the 

 very narrow and very prominent axis in the cephalic shield of the embryos. 



Strenuella (?) Halliana, n. sp. (PI. I, figs 2 a to m.) 



Entire body unknown. 



The head, between the sutures, is truncate, conical (when seen from aboA^e), owing 

 to the strongly-arched test, whicli is much bent downward at the sides. The anterior 

 margin is moderately arched, and the fold distinct, but not prominent. In the broad form, 

 the front slopes downward from the glabella to the front edge, as in Agraulos, and the fold 

 is fainter. The glabella, in the long form, is long, cylindrical to ovate, somewhat pointed 

 in front, somewhat ridged along the axis ; the two posterior furrows arched back, not very 

 distinct ; the third furrow short, faint, transverse ; the fourth, dot-like, scarcely visible. In 

 the broad form, the glabella is ovate to subconical, slightly ridged, furrows faint, and less 

 oblique. The occipital ring extends backward, and terminates in a short, stout spine, 

 which, horizontally, is nearly in the same plane with the top of the glabella ; the occipital 

 furrow is strongly impressed at the sides, but faint in the middle. 



Fixed Cheeks. — These connect in front of the glabella ; they are ridged on the inner 

 side, with a steep slope to the dorsal furrow, and a gentle slope outward. The ocular 

 ridge is distinct in the cast, and the eyelobe short and not prominent. 



Posterior Margin. — Appears short, owing to the bending of its outer angle, it is 

 elevated in the middle of its length into a tubercular prominence ; the posterior furrow 

 is wide and deep, spreading and shallower toward the geual angle. The dorsal furrow 

 is very deep, and goes around the front of the glabella. 



Movable Cheek, Thorax and Pygidium. — Unknown. 



Sculpture. — The outer surface is marked by fine, closely set punctures, and in addition 

 by a few scattered tubercles. 



Development of the Young. — This species, in its narrow form, has been traced back to a 

 small head shield of IJ mm. (PI. I, fig. 2 g) with movable cheek attached, which is remark- 

 able for its high, narrow glabella, narrowed behind, as in the adult of Holometopus and 

 Corynexochus. 



1st Stage (Plate I, fig. 2 h.) — With some hesitation we place here a small shield which 

 has a strong general resemblance to the corresponding stage in Liostracus Oiiangondianus, 

 but it differs from that in the narrower and more prominent glabella divided from the 

 cheeks by heavy dorsal furrows ; this little test exhibits another characteristic of the adult 

 of this species, as compared with the Liostracus above named, in that the occipital 

 furrow is shallow. 



