132 



Surface with obscure concentric strige, from four to six in the width of 

 two^lines, on the anterior half of the shell. In passing backwards, they 

 curve over the oblique carination, and then run with a slope forward, to 

 the straight portion of the hinge line. From the beaks six or eight fine 

 thread-like radiating stride run backwards and downward. They are 

 parallel to and just in front of the carina. 



Length of the specimen described about twenty six lines ; height 

 at the umbones eight and a half lines ; depth of the left valve about three 

 » lines. 



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

 Collector.— T. C. Weston. 



Orthonota angulifera? (McCoy.) 



Sanguinolites anguliferus, (McCoy.) Pal. /'oss. p. 276, pi. 1 k, figs. 19, 20. 



Plate 8, fig. 13 



Description. — Of this species there is only the impression of the anterior 

 half of the right valve in the collection. The anterior extremity projects, a 

 little more than one-half the height of the shell, beyond the beaks. Its 

 surface is marked by six sharply elevated ridges, which, commencing on 

 the hinge line descend obliquely downwards and backwards to the ventral 

 margin. The sixth ridge, from the end, does not quite reach the margin, 

 but turns upwards at an angle of about 80^ and ascends the side of the 

 shell, sloping a httle forwards, for about two-thirds the height. Within 

 the angular space, inclosed by the two parts of this ridge, there are two 

 others, shorter but similarly angulated ridges. From the umbones three 

 obscure concave folds slope backwards, as in venusta. These are crossed 

 by obscure nearly vertical grooves, from the hmge-line downwards, about 

 six of these in two lines. 



This shell seems to be proportionally wider behind than those figured 

 by McCoy, but to differ from them in no other material respect. 



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



Collector.— T. C. Weston. 



MODIOLOPSIS EXILIS. (N. Sp.) 



Plate 8, fig. 5, 5 a. 



Description. — Shell transverse, sub-ovate ; slightly arcuate ; length a 

 little more than twice the height ; hinge-line nearly straight, slightly 

 convex, extending backwards to about the posterior third of the length 

 of the shell ; ventral margin in some specimens gently concave, in others 

 in the anterior half and slightly convex behind ; curved upwards at each 



