at Transactions of the Academy of Science of St. Louss 
without any defined mesial elevation, the greatest convexity 
being in the central part, from which it slopes nearly equally 
in all directions. Beak very small and extending slightly beyond 
the cardinal line, but not incurved. 
“Surface marked by numerous very fine radiating striae that 
are crossed by a few concentric lamellose lines of growth”. 
OBSERVATIONS. 
The type specimens of Atrypa missouriensis Miller were cok 
lected by R. A. Blair of Sedalia, Mo., in 1890 from a small out- 
crop of Callaway limestone on the La Mine River, near Otter- 
ville, Mo. Later Blair selected specimens of this and other asso- 
ciated fossils and forwarded them to S. A. (Sam) Miller of 
Cincinnati for identification. The original lot, excepting those 
sent to Miller, was acquired by the writer and later sent to E. M. 
Kindle for study. They are to be found in the National Museum, 
Ottawa, Canada, Catalogue number 6031. 
_ With the large series collected at Otterville during the last. 
season, it is recognized that Miller’s types are immature spect 
mens of the species. The average measurements of the species 
is as follows—length 28 mm.—breadth 33mm.—thickness 19 mm. 
—number of striae in the space of 5 mm. 7. 
In a recent paper’ it is stated that the types of dérypa 
missouriensis ‘‘appear to have been found in the Cooper lime- 
stone near Otterville, 17 miles east of Sedalia, Missouri. No 
additional specimens that agree with Miller’s figures have been 
found at this horizon.” 
The age of the bed from which Miller’s A. missouriensis was 
collected has been determined by both the writer and McQueen, 
Assistant Director of the Mo. Geol. Survey, as division 2 of 
the Callaway. 
The meager fauna of the Cooper Limestone has been recorded 
by the writer? but no species of Atrypa have been collecced 
from it. 
McQueen and the writer have collected abundant material 
of the species from the exposure within the last three years. 
The lithologic and faunal characters of this outcrop are identical 
with those of zone 2—Spirifer annae zone—of the type locality 
IFenton and Fenton 
, Studies on the genus At Amer, Midland 
Naturalist, Vol. 12, page 15, 1990: s cracat ci te oapag 
2Greger, Amer. Journ. Sci., Vol. 50, July, 1920, pp. 20—24. 
