He is considered one of the more prolific malacologists of the so-called "new school" with Jules René Bourguignat (1828–1892) as his master.

Locard is credited with describing hundreds of zoological species, in particular freshwater mussels and gastropods from the genus Helix.

Among his many publications are articles on the geology of the Lyon region, and treatises on fossil and living mollusks.

[3] In 1877 he published Malacologie Lyonnaise; ou Description des mollusques terrestres & aquatiques des environs de Lyons (1877), based on Ange Paulin Terver's collection of terrestrial and aquatic mollusks found in the vicinity of Lyon.

[4] In 1893 Philippe Thomas published the palaeontology results of the Tunisian Scientific Exploration Mission (1885–86) in six instalments plus an atlas, giving the work of Victor-Auguste Gauthier (sea urchins), Arnould Locard (Mollusca), Auguste Péron (Brachiopods, Bryozoa and Pentacrinitess) and Henri Émile Sauvage (fish).