=23.= DEER CREEK LIMESTONE.[4] Three layers of limestone separated by layers of shale. The total thickness of the formation is fifteen to twenty-five feet. The principal stratum is the uppermost, which is from seven to twelve feet thick. Most of the fossils below are collected from this upper layer. It is a massive, light gray limestone, tinged with yellow. The texture often varies much in a short distance, grading into inclusions or banks of blue argillaceous limestone in which the fossils are excellently preserved. It is best exposed at Calhoun’s Bluffs, in the cut of the Union Pacific railroad three miles northeast of Topeka. _Fusulina secalica_ (Say). _Lophophyllum profundum_ (Milne-Edwards and Haime) Foerste. _Archæocidaris agassizi_ Hall. _Oligoporus minutus_ Beede. _Crinoid_ stems. _Fenestella hexagonalis_ Rogers? _Fenestella_ sp. _Pinnatopora pyriformis_ Rogers. _Polypora distincta_ Ulrich? Probably a new species. It differs from this species in having fenestrules broader and shorter and slightly more slender branches. However, this may be due in a large part to the particular portion of the zoarium of which our specimens are fragments. _Polypora nodocarinata_ Ulrich. _Septopora pinnata_ Ulrich. _Ambocœlia planoconvexa_ (Shumard) Hall and Clarke. _Chonetes granulifer_ Owen. _Crania modesta_ White? _Derbya crassa_ (Meek and Hayden) Waagen. _Derbya keokuk_ (Hall and Clarke). _Dielasma bovidens_ (Morton) White. _Enteletes hemiplicata_ (Hall) Hall and Clarke. _Meekella striaticostata_ (Cox) White and St. John. _Productus cora_ d’Orbigny. _Productus costatus_ Sowerby? de Koninck. _Productus longispinus_ Sowerby. _Productus nebraskensis_ Owen. _Productus pertenuis_ Meek. _Productus punctatus_ (Martin) Morton. _Productus semireticulatus_ (Martin) d’Orbigny. _Pugnax utah_ (Marcou) Hall and Clarke. _Reticularia perplexa_ (McChesney) Schuchert. _Seminula argintia_ (Shepard) Hall and Clarke. _Spirifer cameratus_ Morton. _Spiriferina cristata_ (Schlotheim) Dawson. _Allorisma granosum_ (Shumard) Keyes. _Allorisma subcuneatum_ Meek and Hayden. _Aviculopecten occidentalis_ (Shumard) Meek and Hayden. _Aviculopecten_ sp. _Entolium aviculatum_ (Swallow) Meek. _Myalina kansasensis_ Shumard? _Myalina swallowi_ McChesney. _Pinna peracuta_ Shumard. _Pinna subspatulata_ Worthen? _Bellerophon crassus_ Meek and Worthen. _Trachydomia wheeleri_ (Swallow) Keyes. _Pleurotomaria tabulata_ Hall. _Conularia crustula_ White? (Very large for this species.)