THE FAUNA OF THE ST. JOHN GlîOUl'. 63 



The left (?) valve has a hollow between the tumid body of the shell and the hinge ; 

 in this hollow there is a small foramen anteriorly, and a deep furrow posteriorly ; there is 

 a low inconspicuous tubercle at each end of the hinge line, above the foramen and furrow 

 respectively. 



The notch in the right (?) valve is extended downward as a deep furrow, nearly cor- 

 responding in position to the foramen of the other valve. The inside of the valve has a 

 raised lenticular scar, near the posterior end, and along the inner side of the scar runs a 

 deep furrow ; this furrow is deepest at the upper end, and fades out as it goes round the 

 base of the valve. A deep and wide furrow also extends backward from the notch at the 

 front of the valve, spreading and becoming shallow as it approaches the furroAv at the 

 posterior end of the A'alve. 



It is somewhat doubtful if there are right and left valves to this organism, the forms 

 figured may be variations in shape of the one valve or plate ; but all are easily recognized 

 by the peculiar twisting of the hinge from the plane of the front and lowm* part of the 

 valve. The organism is found in association with the plates of Eocystites prlmœvus, etc. 



Diameter, 1 mm. 



Horizon and LocalUy. In the fine dark shales of Div. l.f, at Hanford Brook, St. Mar- 

 tins. Infrequent. 



VIII.— OSTRACODA. 



BEYRTCHINjE. 



The genus Beyrichia was established in 1851, by Professor MacCoy, on the species B. 

 Kloedeni, and was more accurately defined, in 1855, by Professor T. Rupert Jones. It has 

 become the receptacle for many species of different forms, chiefly from the Silurian rocks, 

 and from all parts of the world. To Professor .Tones, science is indebted for reducing 

 this heterogeneous assemblage to order, so that we can now view them as pertaining to 

 three sections, designated by him respectively asJugosce, Corrttgakc and Simplices. In 1865 

 Professor Jones found good reasons for separating the last named section from the other 

 Beyrichiic as a new genus, Primilia; so that only the two first remain to form the genus 

 Beyrichia, as now vinderstood. We have therefore to deal with these two sections only, in 

 comparing Beyrichia with the resembling forms of the Lower Cambrian of the Acadian 

 region. 



Leaving out of view Beyrichia Holli of the Menevian group, whicli, in the great 

 width of its valves, and in apparently having the anterior end the widest, departs from 

 the true Beyrichite, we find no Beyrichitr in the Lower Cambrian beds, but the place of this 

 genus seems to be taken by the types I am about to describe. These types (genera) agree 

 in having a width of valve c^uite unusual with the Ordovician ' and Silurian Beyrichiœ 

 and one of the genera also differs in having the anterior end of the valve wider than the 

 posterior ; this, in its more evenly tumid valves, may be compared to the Corrugattï- ; the 

 other in its flattened valves and prominent ridges, carries to excess certain peculiarities 

 of the Jugosfe. 



' The system containing the Second Fauna of Barrande. 



