NIAGARA FALLS AND VICINITY 



219 



Leperditia scalaris Jones (Fig. 150) (Grabau. Geol. soc. Am, Bui. 

 11:371, pi. 22) 



Distinguishing characters. Bean-shaped outline; straight hinge 

 line with salient angles; uniformly curved basal margin; an- 

 terior and posterior marginal 



horders; ocular tubercle about 

 a third the length of the shell 

 from the anterior end; strong, 

 elongated fold or " dorsal 

 hump " below the hinge line, in 

 the posterior half of the left 



valve. FIg ' 15 " Leperditia scalaris (enlarged) 



Found in the Manlius limestone of North Buffalo* and elsewhere 

 In Erie county. It is a common species. 



Genus bollia Jones & Holl 



[Ety. : Boll, proper name] 



(1886. An. and mag. not. hist. , ser. 5, 17:360) 



Valves oblong, with rounded and nearly equal ends; hinge line 

 straight, ventral margin curved; surface punctate and bearing a 

 rudely horseshoe-shaped ridge, with a central depression within, and 

 without a semilunar ridge on each side and parallel to the outer 

 margins of the shell, which are slightly rimmed. 



Bollia symmetrica (Hall) (Fig. 151). Beyrichia sym- 

 metrica Hall. (1852. Pal. N. Y. 2 317, pi. 67) 



Distinguishing characters. Extremely small size; thin horseshoe 



ridge, dividing shell into three nearly equal parts; ridges and inter- 



v,_an spaces about equal; outer ridges not continued 



ventrally. 



I A Found in a fragment of weathered Rochester 



J shale, on the talus along the Rome, Watertown and 



Fig. 151 Boilia syni- Ogdensburg railroad cut above Lewiston. As- 



metrica natural size 



and enlarged sociated with the next. (One specimen found was 



larger than the normal, and the horseshoe curve rather thick ven- 

 trally, but not as thick as in B. lata of the Clinton group. This 

 -appears intermediate between the two species.) Also found at 

 JLockport (Hall). 



