This chapter of the "Fauna of British India" series, edited by A. E. ShIPLEY and assisted by GUY A. K. MARSHALL, focuses on the Mollusca, specifically the families Trochomorphidae and Janellidae. The author, G. K. Gude, provides an overview of the systematic classification and descriptions of various species within these families. The text includes detailed descriptions of each species, their original descriptions, and their geographical distributions. Species such as *Trochomorpha castra*, *Trochomorpha ceryx*, *Trochomorpha billeana*, *Trochomorpha frauenfeldi*, *Trochomorpha galerus*, *Trochomorpha hyptiocyclos*, *Trochomorpha percompressa*, *Trochomorpha andamanica*, *Trochomorpha bicolor*, *Trochomorpha iopharynx*, *Trochomorpha lardea*, *Trochomorpha pseudosanis*, *Trochomorpha sanis*, *Trochomorpha subnigritlella*, *Trochomorpha sulcipes*, and *Trochomorpha trilineata* are discussed in detail, including their shell characteristics, size, and habitat. The chapter also covers the subfamily Thysanotinae of the genus *Thysanota*, including species such as *Thysanota tabida* and *Thysanota guerini*. The text highlights the contributions of various malacologists and the challenges in the systematic classification of these species.This chapter of the "Fauna of British India" series, edited by A. E. ShIPLEY and assisted by GUY A. K. MARSHALL, focuses on the Mollusca, specifically the families Trochomorphidae and Janellidae. The author, G. K. Gude, provides an overview of the systematic classification and descriptions of various species within these families. The text includes detailed descriptions of each species, their original descriptions, and their geographical distributions. Species such as *Trochomorpha castra*, *Trochomorpha ceryx*, *Trochomorpha billeana*, *Trochomorpha frauenfeldi*, *Trochomorpha galerus*, *Trochomorpha hyptiocyclos*, *Trochomorpha percompressa*, *Trochomorpha andamanica*, *Trochomorpha bicolor*, *Trochomorpha iopharynx*, *Trochomorpha lardea*, *Trochomorpha pseudosanis*, *Trochomorpha sanis*, *Trochomorpha subnigritlella*, *Trochomorpha sulcipes*, and *Trochomorpha trilineata* are discussed in detail, including their shell characteristics, size, and habitat. The chapter also covers the subfamily Thysanotinae of the genus *Thysanota*, including species such as *Thysanota tabida* and *Thysanota guerini*. The text highlights the contributions of various malacologists and the challenges in the systematic classification of these species.