Principles of Zoological Micropalaeontology, Volume II focuses on the study of microfossils. The book first discusses the nature and characteristics of sponges, including the morphology and main groups of sponge spicules, modifications of the shape of sponge spicules, and arrangement of skeletal elements. The text also looks at octocorals and scolecodonts. The taxonomic relationships of the melanoscleritoids; anatomy of the anterior part of the digestive system tract of polychaeta; and classification of scolecodonts are described. The selection also touches on conodonts. Topics include morphology; phylogeny of lamellar conodonts; and geological distribution of conodonts and their value in correlation. The text also examines ostracoda and echinodermata, including reproduction, sexual dimorphism, ecology of ostracods, and skeletal elements of crinoidea, echinoidea, and holothuroidea. The book also discusses otoliths. Topics include nomenclature and morphology of otoliths; geological distribution and value of otoliths, and history of research. The text is a good source of information for readers interested in fossils.