24O NEW YORK STATE MUSEUM 



quently narrow. Antelateral margin prominent, making the valves slightly 

 aliform at the front angle ; basal margin rather evenlv curved, somewhat 

 transverse beneath ; the posterior margin regularly and somewhat abruptly 

 rounded, not expanded. 



Surface sloping evenly and regularly toward the commissures, rather 

 abruptly to the posterior margin and anteriorly to a broad low depression 

 along the hiatus. The ornamental marking consists of exceedingly fine, 

 somewhat undulating, filiform radial lines; at the lower margin there are 

 seven of these in the space of 1 mm and over the middle of the valve nine 

 lines in the same space. These are interrupted by concentric lines and 

 mav be minutelv crenulated bv finer lines of growth. Sometimes the 

 concentric growth completely obscures the radial markings over most of 

 the pallial region. 



Dimensions A right valve of this species has the following dimen- 

 sions: hight 18 mm, length 18 mm; length of hiatus ix mm - A large left 

 valve measures, hight 30 mm, length 32 mm ; length of hiatus 2Z, mm. 



Habitat. Genesee province ; Naples subprovince. Parrish gully, 

 Naples. A specimen from the lower shales on Pike's creek. Erie co., is 

 also referred provisionally to the species. 



Lunulicardium Prochasma> bickense Holzapfel 



Plate 3. fig. 3-5, 1: 



Lunulicardium bickense Holzapfel, Die Goniatitenkalke von Adorf ; Paleon- 



tographica. 1S82. 2S: 256. pi. 49. fig. 9 

 Lunulicardium 1 a e v e Williams, U. S. Geol. Sur. Bui. 41. 1887. p. 39, pi. 13, 



fig. 5. 6. 8 

 Prochasma bickense Beushausen, Lamellibr. des rhein. Devon. 1895. p. 377. 



pi. 28, fig. 4, 5, 10, 12 



This species, which sometimes attains moderately large size, has 

 an obliquely ovate outline with beak behind the middle line ; sical 

 margin oblique, short, attaining about one half the hight of the valve ; 

 making an apical angle of 30 with the axial line ; direct or slightly 

 incurved and arched. Pallial surface expanded more behind than in front 



