FOSSILS OF THE ACADIAN GROUP. 655 



into six segments. Lateral lobe also divided, furnished with a narrow 

 border. 



This pretty little species I have never detected in the shales from 

 Ratcliffe's Millstream, but it occurs quite abundantly in the shales 

 of Coldbrook. All the specimens I have seen were collected while 

 breaking up some fragments of slate sent me from that locality by 

 Mr Matthew. I am not aware that it is found in St John ; I have 

 never collected it at that locality. It always occurs broken, the 

 cephalic shields and pygidia being separated. 



Note. — Mr Hartt had originally described this species under the 

 new generic name of Dawsonia ; but Mr Billings regards it as a 

 species of Microdiscus of Salter. The surface has a very fine granu- 

 lation not shown in the figure, and the grooves of the border are also 

 more distinct. 



Agnostus Acadiciis, sp. nov. (Fig. 229). Head minute, transversely- 

 elliptical or sub-circular, breadth and length about equal, convex but 

 very depressed, outlines in front and on the sides slightly straight- 

 ened. A narrow flattened and but very slightly elevated border 

 goes round the front and lateral margins. This is separated from 

 rest of shield by a narrow, shallow, flat space, or Ylg. 229. 

 groove, which, on going posteriorly along the lateral 

 margins, loses gradually in width toward the posterior 

 angles of shield, which are rounded. Glabella a little 

 less than two-thirds the length of shield, long elliptical, 

 depressed convex, but more elevated than other parts of 

 the shield, about twice as long as broad, bounded ante- ^gnostus Ac- 

 riorly and laterally by a sharp rather deep groove concentric and pygidi 

 to the outer one above described. A well-marked trans- ""'' "^^^' 

 verse furrow arching backwards separates the anterior third of the 

 glabella as a sub-circular lobe. Posterior part of glabella rounded, but 

 impressed on each side by a little lobe situated in the angle between 

 the cheek-lobe and the glabella. These little lobes are about one 

 quarter the size of the anterior glabellar lobe. Cheeks of the same 

 width throughout, and uniting in front of the glabella, being bounded 

 by the two concentric grooves above mentioned. Posteriorly they are 

 rounded; in width they are rather greater tlian the glabella. They are 

 convex, more elevated along their inner margin, but sloping outward, 

 roundly, and evenly. Glabella witli its lobes project considerably 

 beyond posterior margin. Surface smooth. Pygidium of this 

 species (V) of about the same outline as cephalic shield. The 

 posterior and lateral margins have a sliglit raised border, separated 

 from lateral lobes by a shallow but well-marked groove running 



