208 



Compared 

 with other 

 species. 



Size. Length, 5 to 5i mm. ; breadth 4 to 5 mm. ; depth of each valve 

 about 1 mm. The ventral is about ^ mm. longer than the dorsal. One 

 dorsal has a length of 6 mm. 



Horizon and locality. In calcareous sandy layers with the Peltura 

 fauna (C. 3 b.) at Me Adam shore, Escasonie, Cape Breton. This species 

 was not found in situ, but in loose pieces of thin flag in the shingle of the 

 shore where the trilobites occur : these pieces were very little worn, and 

 therefore near or at the parent ledge. This species may be referred to 

 the Peltura Zone, (C. 36). 



This species is referred doubtfully to Lingulella as it has some characters 

 of other genera. The weak cardinal development is like Leptobolus ; as 

 is the long lateral ridges and advanced (" j ") laterals of the dorsal valve. 

 The spreading vascular trunks of the ventral valve are like Leptobolus 

 and Obolus, as also the advanced "j" lateral. On the other hand the 

 thick shell is quite unlike Leptobolus, but common in Obolus and Lin- 

 gulella. 



This pretty little species is easily recognized by its peculiar transverse 

 sculpture. Lingula tcehiola, Hall, has a similar transverse ornamenta- 

 tion, but is much larger, and flourished at a later period (Clinton 

 group).* 



Lingulella Ella, H. and W., has a somewhat similar sculpture, but is 

 distinguished by its greater size and closer approximation of the vascular 

 trunks of the ventral valve. 



It is only in a few valves out of many that we find distinct muscle 

 scars, enabling us to compare the species with others. Michwitz has 

 determined that the exterior half of the central muscle in the ventral 

 valve of Obolus represents the " 1 " lateral of Lingula.f In this relation 

 it is interesting to observe that the great muscle in L. (?) Escasoni also 

 has a septum partly dividing it ; but there is a separate scar, a small 

 triangular one, at the anterior outer angle of the great muscle, which 

 with more probability may be considered the external lateral or " 1 " 

 muscle ; the large oval muscle would then be the " h " central (with possi- 

 bly the " k " lateral involved), but it would consist of three main strands; 

 for beside the septum across the middle at the back, the scar is divided 

 by a more obscure transverse ridge parallel to the long diameter of the 

 scar. This muscle then may be compared to those of Lingula, etc., having 

 divisional lines. J 



* New York State Geologists' Report. Hall & Clarke, 1891, pi. 1, fig. 8. 



t Mein. Acad. Imp. des Sci. St. Petersburg. Series VIII. Tom. IV., No. 2, p. 79. 



t Introduction to study of Brachiopoda, Hall & Clarke, p. 229 ; 23, and pi. 2, fig 5. 



