[This work has no abstract, it begins with a table of contents, as follows] The Muscles of the Elasmobranchs: Introduction; 1. Selachii; 2. Heterodontus.; 3. Batoidei; 4. Review; 5. Chondrostei; 6. Holocephali. The Muscles of the Bony Fishes: 1. The Muscles of the Branchial Segments; 2. The Constrictor Muscles of the Hyoid and Mandibular Segments; 3. The Hyoid Muscles other than the Constrictors; 4. The Muscles of the Mandibular Segment other than the Constrictors; 5. The Innervation of the Eye Muscles. The Skull in the Elasmobranchs. The Skull in the Bony Fishes: Appendix A. The Lower Jaw In Bony Fishes; Appendix B. The Teeth of Fishes. The Homologies of certain of the Bones in the Skull of the Bony Fishes. The Phylogeny of the Fishes.