Inrertebrata from the Neocomian of Kansas. — Crayin. 9 
tral margin; east marked with a strong, distally narrowing 
and shallowing sulcus which radiates from the beak down- 
ward and slightly forward, becoming obsolete before it reaches 
the ventral margin, and indicatinga corresponding rib on the 
inner face of the valve ; surface of cast marked with crowd- 
ed, fine, concentric, and coarser, rather remote, and evenly 
distributed growth-lines. 
Measurements. — Right 13; length 32 mm. 
Occurrence. — The figure of this species was drawn several years since 
by the writer, who obtained the type and only known specimen from 
dark clay shale in the "Blue Cut" of the A. T. & S. F. railway, on 
Otter creek, a few miles south-southwest of Belvidere. It was associ- 
ated with Cyprimeria i/ntrftt/a Crag., Cardium kansasenst Mk., Tvrri- 
tella seriatim-granulata Roem., Schloenbachia peruviana Von !>.. Spheno- 
tlixfus pedernalis Roem., and other species belonging chiefly to No. '■'> of 
the Belvidere section. 
MACTRA ANTIQUA. sp. nov. 
Shell small, triangular, longer than high, of very moderate 
convexity ; upper anterior margin of either valve, in advance 
of the feebly excavated beak-front, forming nearly a straight 
line a little shorter than the feebly convex line described by 
the supero-posterior margin; anteumbonal and postumbonal 
slopes depressed so as to present a broad and shallow radial 
sulcus, the anterior sulcus separated from the discal surface 
by a slight angulation ; beaks slightly in advance of the mid- 
dle, their apices turned inward and but very little forward: 
hinge narrow; the anterior ^-shaped cardinal tooth of the left 
valve short and stout, its sinus shallow; posterior cardinal 
narrowed above, broad below, the broad lower extremity bear- 
ing on its anterior side a short denticle which imperfectly 
subdivides the cartilage-pit. 
Measurements. — Ilight 23.5; length 27; breadth lb mm. 
Occurrence. Several specimens from the transition between No. land 
No. 3 of the Belvidere section: one to two miles southwest of Belvidere 
stat ion. 
The occurrence is interesting, as the genus Mactra is chiefij charac- 
teristic of recent and N :ene times and is bul sparingly represented in 
the lower Cretaceous, M.occultaoi the upper Jurassic being the onl.A 
species of this genus known to occur earlier than the Neocomian. 
MARGARITA MARCOUANA. sp. nov. 
Shell turbinate, spire moderately prominent; whorls four 
and a half, convex, increasing rapidly in size, the large body- 
