122 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



VISTOIA PRISCA, new species 



Plate 17, fig. 14 



Dorsal shield convex and strongly trilobed, elongate, elliptical in 

 outline. The facial sutures cut the anterior margin almost directly 

 in front of the sides of the expanded front of the glabella and then 

 curve a little outward and backward to the anterior end of the eye ; 

 passing around and above the eye they then slope outward and back- 

 ward with a gentle curve to the posterior margin so as to leave a 

 strong postero-lateral limb. Glabella elongate, clavate in outline, 

 expanded in front and narrowing gradually from about midway to 

 the occipital ring, without glabellar furrows ; occipital ring strong and 

 separated from the glabella by a broad shallow furrow which is con- 

 tinued out across the postero-lateral limbs ; its posterior margin rises 

 at the center and may have carried a spine. Palpebral lobes elongate, 

 prominent and nearly one-half the length of the cranidium. Fixed 

 cheeks of medium width. Free cheeks unknown. 



Thorax with five (5) segments; strongly trilobed and convex; 

 pleural lobes narrow ; pleural segments short with rather blunt 

 backward curving ends ; pleural furrows broad, straight out to the 

 geniculation where they begin to narrow and curve backward with 

 the end of the pleura. 



Pygidium with a strong convex axial lobe extending nearly its entire 

 length; an anterior ring is outlined by a faint narrow furrow that 

 also extends across the lateral lobes just within the anterior margin; 

 no other transverse furrows have been observed. 



Dimensions. — Dorsal shield, length 13 mm., width about 6 to 7 mm., 

 length of cephalon 5 mm., thorax 4 mm., pygidium, .4 mm. 



Surface of outer test appears smooth. 



Observations. — The type and only specimen of this species occurs 

 in a calcareous shaly rock ; it is slightly compressed laterally which 

 makes it more than naturally convex. The expanded glabella, large 

 eyes and narrow free cheeks suggest Corynexochus ^ as do the thoracic 

 segments, but the pygidium with its elongate outline and smooth axial 

 and pleural lobes gives the impression of a pygidium of Eodiscns 

 with a smooth axial lobe. 



Other specimens of this species will undoubtedly be found when 

 the shales and limestones above the Lower Cambrian sandstones of 

 the Robson District are searched for fossils. 



^ Smithsonian Misc. Coll., Vol. 64, No. 5, 1916, pis. 55-57. 



