251 



Fig. 166. Modiomorpha sub-alata. Three right valves and one left valve, showing 

 variations (from Hall). 



abundance); in the Trildbite beds and the shales above, at 

 Section 8, and on the Lake Shore (common); and in the 

 Pleurodictyum beds (rare). 



Modiomorpha alta. (Conrad.) (Fig. 167.) (Pal. X. Y.. 

 Vol. V., Pt. I., p. 278, Pis. XXXVII., LXXX.) 



Distinguishing Characters. — Broad rhomboid-ovate out- 

 line; curved posterior margin; elevated posterio-dorsal 



Fig. 167. Modiomorpha alta. Right and left valves of different individuals (from Hall >. 



portion ; produced, rounded, but ill-defined, anterior portion : 

 irregular surface stria?. 



Found only in the middle Pleurodictyum bed, in Avery's 

 Ravine (rare). 



Genus GOXIOPHORA. Phillips. 



[Ety. : Gonia, an angle; phoros, bearing.] 

 (1848: Memoirs Geol. Surv. Gt, Britain, Vol. II., Pt. I., p. 264.) 

 Shells with equal, but very inequilateral, valves, rhom- 

 boidal or trapezoidal in outline, obliquely truncate behind. 



