195 



clearly separable from the other, or from the central scars. *n the dorsal 

 valve the position of the middle and outside laterals is shown, but not 

 their form or size. The transmedian scars in the ventral valve are seen 

 just back of the anterior laterals, but they have not been observed in the 

 dorsal valve, owing to the imperfection of the shell. 



Sculpture. The surface of the shell is marked by concentric strise, and Sculpture, 

 undulations of growth, over which there is a series of very fine elevated, 

 sharply undulating inosculating lines that form a minute, irregular net. 

 work over the surface, very much like that of 0. (Lingulella) etta. Where 

 the lines are strongly elevated the effect is that of a minutely granulose 

 surface. When the thin outer layer of the shell is exfoliated the surface 

 of the various inner layers is minutely granulose in addition to the 

 flattened, radiating strise and concentric lines of growth. Interior. The 

 interior surface of both valves is often marked by concentric lines of 

 strong pits or punctse, very much as in 0. Lingulella davisi. In some 

 specimens the lines of punctse extend over the surface of the visceral 

 cavity so as to obscure the vascular markings and muscle scars. In some 

 examples only a few scattered punctse occur, while in others they are 

 present over nearly the entire surface. The small shells are thin, but the 

 larger ones are built up of a very thin outer layer and several inner layers 

 or lamella that are more or less oblique to the outer surface, especially 

 over the anterior and lateral portions of the shell. 



Size. One of the largest ventral valves has a length of 21 mm., with 

 a width of 18 mm. A dorsal valve 16 mm. in width has the same length ; 

 other example, are a litte wider than long. 



Formation and locality. Middle Cambrian. Upper Paradoxides beds, 

 Siliceous shale and thin bedded sandstones west side of McLean brook, 

 above Marion bridge, Salmon river. Gillis hill, 13 miles south of 

 Marion bridge, Cape Breton island, Nova Scotia. [The locality on Mc- 

 Lean brook in on the horizon C. 2 b. G. F. M.] 



Observations. This "appears to be a representitive of 0. (L.) acumi- Comparison 

 natus which is so abundant in the Middle Cambrian of the Upper Missis- w 

 sippi valley, and the passage beds between the Cambrian and Ordovician 

 adjoining the Adirondack mountains of New York. It differs from that 

 species in its greater average width and in its surface characters." 



The above being the description of a shell from McLean brook, Mira 

 river it is clearly not L. Gregwa which occurs at another locality and in 

 lower terrane. A thousand feet in vertical thickness of sandstones, shales 

 and flags separate the the two species and three distinct Cambrian faun- 

 as intervene. The " species " is really a variety of Lingulepis Starri of the 

 13A c. R. 



