Jura,, Neocomiaii and Chalk of Arkansas. — Marcou. 359 
rounded back and its indistinct flexuous line on tlie side, it 
is a true discoid Ammonites, related to the three rounded-keel 
Ammonites litocerus yo and contejeani Thurmann ; three 
species of the upper Jurassic system of central Europe rang- 
ing from the Ammonites {Oppelia) tenuilohatas zone to the 
Portlandian. It has also some resemblance to Oppelia 
latilohata Waagen of the lower Oolite of Poland. The locality 
of that Jurassic Ammonite is at the mouth of Caney creek, 
branch of Prairie creek, near Murfreesboro, Pike county, Ar- 
kansas. 
Pleurocera stromhlformls Schloth. It resembles a Cerlthiuni 
or a Nerinea, related to Cerithitim pseudoexcavatum de 
Loriol, as well as to Nerinea nodosa Frederick A. Roomer and 
Nerinea speciosa Voltz ; all upper Jurassic gasteropods of 
Boulognc-sur-Mer, Hanover and Porrentruy. The fig. 7a, 
Plate ir, of Mr. Hill, shows the opening with a fold so common 
in Nerinea. It will require better si)ecimens and better 
figures before dividing the genus of that most common and 
characteristic shell of the Arkansas and Texas Trinity beds. 
Vivipara cossatotensis Hill, the specimens being only 
"poorly preserved casts," have deceived the author; they do 
not belong either to the genus Vivipara., nor to Liaplacodes, 
but to Natica. The species is allied to Natica zangis 
d'Orbigny of the lower Oxfordian. Buccinopsis conradi 
Hill ; it is almost identical in general contour with the figure 
oi Buccinopsis parry I Conra.d.^' Professor Hill's fossil is a 
Natica, allied to Natica athleta d'Orbigny, of the Portland- 
ian of France. It differs greatly from Buccino2)sis parryi 
in the mouth, and on account of ribs on the spine. 
Ostrea franklini Coquand. This species was named in 
my library in Paris in 1868, by Coquand, who came to ask me 
the permission to study my American Ostracw, for his "Mon- 
ographic du genre Ostrea," in two parts. Coquand published 
only the first part, the Cretaceous species, the second part 
being left in manuscript imfinished. Ho recognized that the 
GryphiEa tueumcarii and the Ostrea marsMi of the 
Tucumcari area (New Mexico) are Jurassic species, and he 
did not put them in the Cretaceous part of his Monograph, 
placing there only the GrypJioia pitcheri typical form, as 
described and published by Morton, F. Roomer and Marcou. 
After studying mv specimens, Cotpiand asked me for any 
