686 PROCEEDINGS OF THE NATIONAL MUSEUM voi..xxiii. 



curve corresponding to the pedicle groove of the larger valve is wide 

 and clearh' defined. 



The casts of the interior of the valves show almost no traces of the 

 vascular markings or muscle scars. Only the anterior lateral muscle 

 scars have been observed in the ventral valve. 



Observations. — This fine species occurs in great alnindance in the 

 upper beds of Little Bell Island, associated with O. (Z.) hell id us., and 

 also in the higher beds on Great Bell Island, a little below the layers 

 carr^nng Linguloholus affinis and L. sjnssus:. Although found at 

 .some little distance above the horizon in which I collected a species of 

 Olenus, I refer the horizon to the Upper Cambrian. 



This species appears to be clearlv distinct from any yet described. 

 It ma}' be compared with 0. (Z.) davisi in relation to its size and out- 

 line, but not in other respects. 0. (Z.) Jejyh ranges from the Lingula 

 flags into the Tremadoc. 



This is one of the most abundant forms in the shales and interbedded 

 sandy hunn-s of Cape Breton Island. Mr. Matthew described a com- 

 pressed dorsal valve occurring in shale as Llngidella concinna, and 

 some fragmentarv shells occurring in limestone as Lingida ? lens. 

 AVith his two types before me in comparison with a large series 

 collected by Mr. S. Ward Loper at the same or near-l^y localities, 

 I find that the two species merge into one and that they are identical 

 with 0. (Z.) hellus as it occurs in Newfoundland. 



The diagrammatic figures of O. (Z.) lens as given bv Mr. Matthew 

 are misleading. The material from which his description was written 

 and figures drawn is badly crushed and broken, the fragments of 

 shells being embedded together in the limestone. None of the speci- 

 mens show the apex of the ventral valve. The one used in illustra- 

 tion by Mr. Matthew has the apex broken away, and the shell is 

 somewhat compressed lateralh'. The diagrammatic drawing of the 

 dorsal valve is also inaccurate. His illustrations of the outer surface 

 appear to be based on specimens from which the true outer surface 

 has ))een exfoliated. 



Among the collections made 1>y ]SIr. Loper there are ti large number 

 of shells crushed and crowded together, very much as is the typical 

 material used by Mr. Matthew. There are, however, in the accom- 

 panying shales large numbers of individual specimens that are beau- 

 t-ifulh^ preserved, which illustrate the outline and convexity of the 

 shell. The series illustrates the growth of the shell, also the various 

 form:» ill which it occurs owing to differences in the sediment in which 

 it has been eml^edded. The material collected by jNIr. Loper came 

 from several horizons of the Upper Camljrian. Mr. Matthew assigns 

 Lingulella concinna to the Dictyonema zone and Lingida lens to the 

 Parabolena zone of the Cape Breton section. 



Formation and locality. — Upper Cambrian. Arenaceous shales of 



