FOSSILS OF THE ACADIAN GROUP. 645 



very narrow, and marked by fine parallel longitudinal etrise. Hinge- 

 plate bearing two slight incurved internal processes. Ventral valve 

 more arched than the dorsal, with a narrow flat margin produced 

 in the plane of the valve. Hinge-area triangular, concave, and 

 marked with fine parallel lines. Umbo elevated above hinge-line 

 about one-fourth of length of shell. Foramen triangular and 

 of moderate size. Surface ornamented by about thirty prominent 

 rounded radiating plicte, increasing in width towards the margin, 

 becoming less elevated and slightly curved toward the ears, crossed 

 by a immber of distinctly marked, concentric, squamose lines of 

 growth, and numerous fine concentric striaj. The radiating plicre 

 increase by bifurcation, wliich takes place at about one-third the dis- 

 tance from the umbo to the margin. Rather common in the Trilobite 

 shales, Ratcliffe's Millstream, and St John. Collected by N. B. 

 Survey and J. W. Hartt. The figure does not show the fine con- 

 centric lines. 



Orthis, n. s. There appears to be a second species in the St John slates ; 

 but the material at hand does not at present warrant its description. 



Conocephalites Baileyi, Hartt. MS. Head transversely semi- 

 elliptical, half as long as wide ; anterior margin in front more or less 

 straight, posterior margin quite straight ; posterior angles of cheeks 

 slightly rounded and unfurnished with spines. Facial suture never 

 visible ; anterior margin of shield with a narrow very elevated border, 

 which Is widest and most elevated In front, and grows narrower and 

 lower posteriorly, becoming obsolete, or nearly so, at the postepor 

 angle of the shield. This border is separated from the other part 

 of the shield by a deep, rather wide furrow, which is deepest in 

 front but grows shallower as the anterior border loses in height 

 going posteriorly. General form of shield convex, but much 

 depressed. Glabella more depressed than the cheek, sub-triangular, 

 depressed convex, broadly rounded in front, and separated from the 

 cheeks and front by a deep Avell-marked furrow ; width at base equal to 

 length, which last is about 7-lOths that of shield ; very much narrowed 

 In front. Lateral bounding furrows inclined to one another at such 

 an angle as would cause them to meet if produced to the middle of 

 the front margin of head. Occipital furrow deep and well marked, 

 slightly arched forward in middle, and cuvving downwards and forwards, 

 growing narrower at the extremities, and less deeply cut than the bound- 

 ing furrow of the Glabella. No lateral glabellar furrows, or very 

 slightly marked, never seen on casts. Occipital ring more elevated, and 

 rather wider in the centre ; bent forward at the sides ; narrow, with a 

 very low spine-like tubercle in the centre. Posterior furrow moderately 



