Weller — Kinderhook Faunal Studies. 36 



rounded umbonal ridge extends from the beak to the poste- 

 rior basal extremity; anterior to this ridge the shell is moder- 

 ately convex from the dorsal to the basal margins, becoming 

 flattened anteriorly ; posterior to it the shell is slightly con- 

 cave, becoming compressed towards the margins. Just below 

 the dorsal margin and subparallel with it, posterior to the 

 beak, there is a long stright hinge tooth, represented in the 

 specimens by a groove. The whole surface of the shell is 

 covered with more or less discontinuous and irregular con- 

 centric ridges, with the posterior slope smoother than the 

 remainder of the shell, 



Remarks. The species is most nearly allied to P. mis- 

 souriensis SwalL, described from the Kinderhook Group of 

 Pike County, Missouri, and in order that a comparison 

 between the two species may be made, a copy of Meeks* 

 illustration of the specimen of that species is introduced on 

 plate II. The Northview species differs from P. missouriensis 

 in its more rounded umbonal ridge, in its slightly arcuate 

 posterior margin which meets the basal margin with a less 

 acute angle and in the larger angle between the umbonal 

 ridge and the basal margin. 



Fragments of this shell are not at all uncommon in the 

 Vermicular Sandstone at Northview, but only a small number 

 of specimens approaching perfection have been found. 



Promacrus cdneatus Hall. 



PI. III. f. 2. 



Shell below medium size for this genus, attaining a length 

 of about 85 mm., a little more than three times as long as 

 high, compressed anteriorly but more convex posteriorly, the 

 beaks situated at a point posterior to the middle. Basal mar- 

 gin nearly straight, anterior margin narrowly rounded at the 

 extremity; posterior margin straight, oblique, meeting the 

 basal margin at an acute angle of about 60° ; dorsal margin 

 with a long, nearly straight slope in front of the beak, 

 straight and slightly sloping back of the beak. The posterior 

 umbonal ridge sharply carinate from the beak to the posterior 

 basal angle, the posterior slope short, concave. Surface 



» Am. Jour. Conch. 7. pi. I.f.l. (1871). 



