EARLY DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA IOO. 



margin. Umbonal ridge conspicuous, blunt and broadly curved, exterior 

 with low irregular concentric folds. 

 Locality. Presque Isle stream. 



Leptodomus corrugatus Clarke 



Plate 28, figure 6 



Leptodomus corrugatus Clarke. N. Y. State Mus. Rul. 107. 1907. p. 224 



Shell small, beak at the anterior third of the hinge, outline subelliptical, 

 posterior slope gently sulcate, smooth, anterior surface coarsely corrugated 

 and over the median area these anterior ridges duplicate, there being on the 

 whole on the lateral slope two ridges for every one on the anterior surface. 

 Median surface slightly depressed. 



Locality. Presque Isle stream. 



Palaeoneilo 



There are several species of this genus all of them found in the 

 Presque Isle stream fauna, and most of them are characterized by an 

 oblique posterior cincture, making a sinuous postlateral margin. This par- 

 ticular style of expression typified a group of shells which seems almost 

 everywhere, except in New York, to emphatically characterize the arenaceous 

 Lower Devonic. Such species occur in the Coblentzian sandstone in very 

 notable abundance ; reference may be had to a long list of these described 

 and figured by Beushausen, Maurer and others. A similarly striking devel- 

 opment of these sinuous Palaeoneilos is notable in the Lower Devonic 

 Maecuru sandstones of Para and specially in the Bokkeveld beds of Cape 

 Colony, South Africa. 



Palaeoneilo orbignyi Clarke 



Plate 28, figures 20-23 



Palaeoneilo orbignyi Clarke. Palaeozoic Faunas of Para. Eng. ed. from Archiv. 

 do Mus. Nacionial do Rio de Janeiro. 1900. 10: 74, pi. 8, fig. I4~r7 



This species described from the lower arenaceous Devonic of the 

 Maecuru river, Brazil, is reproduced in the form here figured, which is 

 distinguished from its associates and from other species of this time by its 

 highly convex valves with arched umbones, incurved beaks and strongly 

 sulcate and sinuate posterior surface. The hinge has not been observed in 

 the original material and from the specimens in hand we observe that it 

 bears a posterior row of ligament pits which begin minutely beneath the 

 beak where this posterior limb is separated from the anterior by a faint 

 oblique line ; these pits at first vertical, rapidly become oblique and coarse 

 backward, slightly chevroned but losing their geniculation toward the end 

 of the row at the inner edge of the posterior adductor. The pits of the 



