The malacological collection consists of dry shells and wet preparations of mollusks. It consists of three sub-collections: the Grüll collection, the Cvitanović collection and the central collection of mollusks. The authors of the Grüll and Cvitanović collections stored all the shells of the same species, regardless of the date or place of the finding, in the same boxes. Each of these boxes, which sometimes contains dozens of shells, has one inventory number and is registered as one item. Thusly one species in the Grüll and Cvitanović collection has only one inventory number. In the central collection of mollusks the shells are classified according to the place and date of finding so that there exist a greater number of items of the same species which are attributed with different inventory numbers.
The Grüll sub-collection is a collection of the shells of bivalvia, gastropods and cephalopods which was gathered by the amateur Joseph Grüll and which dates from the end of the XIXth century and the beginning of the XXth century. It is believed to have been made in Lukoran on the island of Ugljan. It was purchased in 1972. Specimens do not have data about the place of the collecting or about the person who collected them. These facts are detrimental to the scientific relevance of the collection and give it only exhibition, comparative and regional value. Blaž Cvitanović’s malacological collection was formed between 1905 and 1916 in Veli rat on the northern tip of Dugi otok. Don Cvitanović stored specimens of shells in carton boxes on which he indicated the species name and its rarity. The boxes were kept in a cupboard with 60 drawers which he had made in 1910 according to his own design. The cupboard with the original boxes is in safekeeping together with the malacological collection. In February 1964 the Natural History Department of National Museum Zadar purchased the cupboard with drawers in which 400 species of mollusks with three times that number of specimens were stored. The central collection of mollusks is still being enlarged and the number of species and specimens continuously grows. It is mostly the fauna of the Zadar area that is being collected.