NIAGARA FALLS AND VICINITY 179 



Genus pholidops Hall 



[Ety.: <poXi<s, a scale] 



(1859. Pol- N. Y. 3 489; 1892. Pal, N. Y. v. 8, pt i, p. 155) 



Shells small, with equal valves, patella-like in outline; inarticulate 

 and unattached, without pedicle opening; position of apex variable; 

 edges of valves flattened where they meet, and on the interior are 

 elevated areas for attachment of muscles, etc. In molds of the in- 

 terior, a strongly marked impression of this callosity appears. 



Pholidops squamiformis Hall (Fig. 82). O r - 

 bicula ? squamiformis Hall (1852. 

 Pal. X. Y. 2:250, pi. 53, fig. 4a-b) 



Distinguishing characters. Depressed oval 



. . . Fig. 82 Pholidops squam- 



form; squamous concentric striae, most marked iformis natural size and 



enlarged 



on anterior slope. 



Found near the middle of the lower Rochester shales at Niagara. 

 Also at Lockport (Hall). 



Genus dictyonella Hall 

 [Ety.: di-z-vov, net] 



(1867. N. Y. state cab. net. hist. 20th an. reft, p. 274; 1893. 

 Pal. N. Y. v. 8, pt 2, p. 307) 



Shell subtriangular in outline with biconvex valves, pedicle valve 

 having a broad median sinus, and brachial valve a corresponding 

 fold; beak of pedicle valve acute and arched over that of brachial 

 valve, though not closely appressed against it; a short, triangular 

 deltidium depressed within the cavity of the pedicle valve ; teeth long, 

 marginal and ridge-like on the diverging cardinal slopes and fitting 

 into narrow marginal grooves on the brachial valve; brachial valve 

 with a strong median septum. Exterior covered by a coarse net- 

 work of superficial cells, usually hexagonal, sometimes circular in 

 outline. A triangular area at the umbo of the pedicle valve is 

 destitute of this reticulation. 



Dictyonella corallifera Hall (Fig. 83). Atrypa coralli- 



fera Hall (1852. Pal. N. Y. 2:281, pi. 



( Jl 58 ' fig ' 5a_t) 



#; ' Distinguishing characters. Form rhom- 



boidal to subtriangular, base often nearly 



( c',''- straight; broad and strung sinus and fold; 



S <'" : r '\ ' 



reticulated or pitted surface, the space be- 



Fig. 83 Dictyonella corallifera with , . . 



surface enlarged tween the pits often punctate. 



Found in the Bryozoa beds of the Rochester shale at Niagara. 

 Also at Lockport (Hall). 



