Specific substrata or locations used for oviposition and external and internal structure of egg capsules produced by small prosobranchs from seagrass beds and coastal splash pools are described. Included are Tricolia affinis affinis (C.B. Adams, 1850), T. thalassicola (Robertson, 1958) T. bella (M. Smith, 1937), Puperita pupa (Linne, 1767), Smaragdia viridis viridemaris (Maury, 1917), Littorina mespillum (Muhlfeld, 1824), Alvania auberiana (Orbigny, 1842), Rissoina catesbyana (Orbigny, 1842), R. bryerea (Montagu, 1803), Zebina browniana (Orbigny, 1842), Rissoella caribaea (Rehder, 1943), Caecum nitidum Stimpson, 1851, Marginella aureocincta (Stearns, 1872, and Granulina ovuliformis (Orbigny, 1841). Populations of mature adults were collected at locations in Florida and Bimini, Bahamas, acclimated in the laboratory, and allowed to spawn in polystyrene Petri dishes. Descriptions were based on egg capsules from 10 spawning events.