Observations on Terataspis grandis, Hall, the largest trilobite known, is a unique book written by the eminent scientist John Mason Clark. This research paper focuses on the species Terataspis grandis, which is the largest known representative of trilobites. The author examines in detail the morphological features of this ancient sea creature, considers its role in the natural environment and its importance for understanding the evolution of living organisms. The book contains dozens of illustrations and is accompanied by data from leading scientific studies. "Observations on Terataspis grandis, Hall, the largest known trilobite" is an essential part of the library of any specialist in the field of paleontology and evolutionary biology.