Maryland Geological Survey 337 



respects tliey resemble BoUia lata Hall ; ^ but they are larger, and the 

 central curved ridge is much thinner at its carve, whereas in the specimens 

 from New York State the curve is thicker just there, and is not so sym- 

 metrical throughout as in the Pennsylvania specimens. Hence I prefer 

 to regard the latter as specifically distinct, and to adopt Prof. Claypole's 

 MS. specific name (having reference to the hoof-like ridge), than to refer 

 them to Bollia lata. A hollow cast of the outside, and one presumably 

 perfect valve give evidence of a smooth exterior. 



The slight variations in the shale and proportions of the curved sub- 

 central ridge and of the marginal ridge are well shown in the figures 10- 

 13." Jones, 1889. 



Occurrence. — Romney Formation, Onondaga Member. Williams 

 Road, 3^ miles southeast of Cumberland; Tonoloway. 



Collection. — U. S. National Museum. 



Bollia obesa Ulrich 



Plate XLIV, Fig. 9 



Bollia obesa Ulrich, 1891, Jour. Cincinnati Soc. Nat. Hist., vol. xiii, p. 189, 



pi. xiv, figs. 5a, b, c. 

 Bollia ohesa Kindle, 1912, Bull. U. S. Geol. Surv., No. 508, p. 114, pi. ix, fig. 8. 



Description. — " Size of valve : Length, 1.52 mm. ; height, 0.98 mm. ; 

 thickness, 0.5 mm. Carapace subpentagonal, ends nearly equal, strongly 

 curved, back straight, short, dorsal angles obtuse, ventral edge produced 

 in the middle. Marginal portion of valves thick, causing them to appear 

 unusually ventricose. Horse-shoe ridge unsymmetrical, with bulbous ex- 

 tremities, the anterior knob oval, and reaching the dorsal edge> the pos- 

 terior one larger, more nearly round, and terminating a short distance 

 within the dorsal margin. 



"This species is not likely to be mistaken for any other known to me. 

 Though clearly a true Bollia, it is veiy different in its general appearance 

 from the associated B. singula, Jones. 



' Paleontology of New York, vol. ii, 1852, p. 301, pi. 66a, figs. 10a, b, d (not 

 c and e) , also some in British museum. I may here mention that I have to refer 

 lata and syynmetriea to Bollia, and spinosa to Aechima. 



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