The Lower Cretaceous Gryph?as of the Texas Region, Issue 151

The Lower Cretaceous Gryphæas Of The Texas Region, Issue 151 by Robert Thomas Hill and Thomas Wayland Vaughan examines the Lower Cretaceous gryphate oysters of the Texas region, clarifying historic confusion and presenting a comprehensive taxonomy, development, and evolution of the group. The work surveys the classification and stratigraphic occurrence of Gryphaea species, distinguishes Morton’s G. pitcheri from related forms such as corrugata, navia, washitaensis, and mucronata, and traces their horizons within the Comanche and Washita divisions. It recounts the long historical debate among 19th-century paleontologists (Marcou, Hall, Roemer, Conrad) and outlines how large series and growth stages reveal distinct species and varieties. The authors describe new species, Gryphaea wardi and Gryphaea marcoui, and a new form G. washitaensis Hill, among others, and discuss the phylogeny of the group. The monograph provides descriptive plates, geologic sections, and implications for stratigraphic correlation and practical applications such as artesian-water exploration.