121 



of them. In front of the posterior adductor muscle on each side of the 

 valve, there is a low ridge extending forward as far as the scars of the 

 central muscles : at and in front of these ridges the imprint of the main 

 vascular trunks is visible, extending forward toward the median line. 



The interior of the dorsal valve has a broad scar (posterior adductor 1) 

 just in front of the striated hinge area, and on each side of the hinge are 

 impressions of sliding muscles. The central muscles are indicated by a 

 group of small pits near the centre of the valve ; of these the anterior 

 adductors are oval and somewhat apart at the mid-length of the valve ; 

 the anterior adjusters are indicated by a pair of small rounded pits, a 

 little in advance of those last named and closer together. A faint line 

 (indicating the border of the splanchnoccele ?) includes these scars and 

 runs back towards the posterior part of the valve. Extending forward 

 from near the cardinal area on each side are the lateral ridges and the 

 imprint of the vascular trunks, as in the ventral valve, but here more 

 distinct and bearing a number of branches directed, some inward and 

 some outward. 



Sculpture. The external surface of the valve of this species is marked 

 by fine concentric lines, and fainter radiating lines ; there are also at 

 intervals, concentric growth lines, and less distinct undulations of the 

 shell, radiating from the umbo. 



Size. Dorsal valve. Length and breadth, each about 11 mm. The 

 ventral valve is about 1-5 mm. longer. 



Locality. McFee's point, (i. e. Young point) George river, Cape 

 Breton ; collected by Messrs. Weston and Robert, of the Canadian Geo- 

 logical Survey. 



The plan of the muscular scars of this species is very nearly that of 

 Obolus Quenstedti of A. Michwitz, found in Esthonia, Russii, and as we 

 find a shell in the Lower Cambrian of the St. John Group which possesses 

 all the essential characters of an Obolus, but differs from this shell, we 

 fully agree with Messrs. Hall and Clarke that 0. Quenstedti could, with 

 propriety, be excluded from Obolus ; whether it should go into Lingulella 

 will be better known when the internal features of the species L. Davisii, 

 the type of that genus, are more fully described." 



Additional note on L. Selwyni. 

 A comparison of the size and outlines of the valves of this species Additional 



, characters of 



shows it to have been a wide one. The vascular trunks of the ventral Lingulella 

 valve are half as far apart as the width of that valve. This species has Selw y m - 

 marked growth grooves on the outer surface, always outside of the 



