312 NEW YORK STATE MUSEUM 



ginate by the posterior sinus. Postcardinal slope long and oblique. Sur- 

 face convex on the umbones, sloping rather abruptly to the front margin ; 

 behind, the surface is sinused by a broad, low depression which brings into 

 prominence a postmedian umbonal ridge. Specimens from the shales and 

 the barite replacements indicate that the surface was smooth or with obscure 

 concentric growth lines. This condition is clearly shown in most of our 

 figures. Only one, an incomplete replacement, shows that over the poste- 

 rior part of the shell the concentric lines are well defined and elevated, but 

 not to such degree as in other species. On the interior, anterior and poste- 

 rior muscular scars, with thickened inner walls, are at times very sharply 

 defined. The cardinal area is broadly arched, the denticuiations are all 

 vertical and decrease in size beneath the beak. 



Dimensions. A specimen of full size has a length of 10 mm, hight 6.5, 

 thickness through conjoined valves 3.5 mm. 



Habitat. Genesee province ; Naples subprovince. Not uncommon in 

 the soft shales of Livingston, Ontario and Yates counties. Chautauqua 

 subprovince. A single specimen has been obtained at Pontiac, Erie co. 



Palaeoneilo muricata sp. nov. 



Plate 15, fig. 14, 15 



Professor Hall described several specimens of Palaeoneilo from the 

 New York Devonic which bear two instead of one posterior sulcus outside 

 of the cardinal slope, P. bi sulcata from the upper Chemung of Elmira, 

 P. muta and P. perplanaof the Hamilton and Ithaca faunas, and of 

 these P. bi sulcata and P. muta show evidence of having had the con- 

 centric lines of the surface produced and lamellate. 



The little species now before us can hardly be referred to any of these 

 shells, as it is persistently of much smaller size and of somewhat different 

 outline. Its strikingly latnellose surface ridges were probably equaled in the 

 species cited, specially P. mut a, but these characters have not been well 

 retained in the shale specimens with which alone we are acquainted. 

 Palaeoneilo muricata covers small subelliptic shells, subtruncate pos- 

 teriorly ; beak prominent at anterior third of cardinal line, anterior extrem- 



