670 NEW YORK STATE MUSEUM 



with strong concentric and apparently regular, radiating corru- 

 gations. The latter become obsolete toward the lateral margins. 

 The extreme thinness of these corrugated shells suggests that 

 they are much macerated, and only one shell layer preserved. 

 As similar corrugations occur in exfoliated and compressed 

 specimens of Lepto bolus insignis, where the charac- 

 teristic, fine radiating striae of the inner layer develop under like 

 conditions into a system of wrinkles, the supposition seems legiti- 

 mate that these corrugations are only the result of maceration 

 and compression of an originally more convex shell. This sup- 

 position is strengthened by the occurrence of less corrugated 

 shells, furnishing various transitions to thicker, smooth, unex- 

 foliated valves. The latter, instead of becoming corrugated, 

 yielded to the pressure by breaking radially in two or more seg- 

 ments {see fig. 12). 



The presence of a strong median septum, a pedicle-groove, 

 traces of curving laterals and a posteriorly situated median mus- 

 cular scar in the brachial valve, as well as of a narrow pedicle- 

 groove below the beak of the pedicle-valve, indicate its position 

 in the genus Leptobolus. 



It differs from all other species of Leptobolus by its 

 larger size. Young valves closely resemble specimens of Lep- 

 tobolus insignis, but differ in being less convex, having 

 a less prominent beak, a thinner shell and specially a more regu- 

 lar and finer concentric striation. 



Dimensions. The largest specimen observed attains a width 

 of 10.2 mm and a length (not fully preserved) of 8 mm. 



Lower Trenton. Normans kill shales. Kenwood and Glen- 

 mont, near Albany, Mt Moreno, near Hudson. 



SSchizotreta papilliformis sp. n. {see pi. 1, fig. 

 3-5) 



A third very rare form among the brachiopods of the Normans 

 kill shales has been recognized as a new species of S c h i z o - 

 t r e t a . 



Diagnosis. Pedicle-valve subcircular, depressed conical, slop- 

 ing equally in all directions, beak abruptly projecting just behind 



