135 



ridges, from two to four in the width of two Hues. These are rounded on 

 the upper part, but become more acute towards the margin. On the sides 

 of the shell backwards to the carina, the surface is smoother, but still the 

 ridges are obscurely indicated. There is also a set of very fine striae on 

 and between the ridges. The posterior portion of the shell behind the 

 carina is marked chiefly by the fine stride. There are also obscure indi- 

 cations of a few radiating strioe, extending from the beaks towards the 

 ventral margin, oblicjuely backwards. 



Of this species, only two specimens are in our collection. The right valve 

 of one of these is two inches in length and nine lines in height, (allowing 

 for a small portion concealed in the matrix.) Depth of both valves 

 about seven lines. The other specimen (pi. 8, fig. 7) two and a half 

 inches in length ; height eleven lines ; depth about three lines. 



This latter differs from the first, in having the space behind the carina 

 gently convex. It may be a distinct but closely aUied species. More 

 specimens would be required to decide this question. 



Locality and Formation. — Arisaig, Nova Scotia. Upper Silurian. 



Collector.— T. C. AVeston. 



GONIOPIIORA CONSIMILIS. (N. Sp.) 

 Plate 8, Fig. 8. 



Description, — Semi-ovate ; length a little more than twice the height ; 

 greatest height at about one-third the length from the anterior extremity ; 

 beaks nearly terminal, closely incurved, situated at about half the height 

 of the shell. On a side view, (placing that portion of the shell, which lies 

 below the umbonial ridge, vertically) the outline of the anterior, dorsal 

 and posterior margins together, constitute an almost continuous semi-ovate 

 curve, most obtuse and uniformly rounded in the anterior half and 

 descending with a gently convex or nearly straight slope from about the 

 mid-length to the lower posterior angle. With the plane of the entire 

 margin of the shell vertical, a small portion of the hinge line is seen 

 above the ridge, extending back about two-thirds the length ; thence the 

 posterior margin descends with a gently convex slope to the lower angle. 

 The umbonial ridge is very prominent; its edge not acute but truncated 

 to the width of half a Hne or a little more ; in one specimen it seems to 

 have groove running along its whole length. The anterior extremity pro- 

 jects about two fines beyond the beaks. The ventral margin is nearly 

 straight or gently concave, the anterior fifth curving upwards and a small 

 portion at the posterior extremity curving downwards. 



Surface (of the specimen figured) with very fine transverse strite six to 



