Although the top shell Turbo (Batillus) cornutus (Turbinidae) is a well-known and industrially important shellfish species in Japan, the diploid chromosome number and karyotype of this species have not been previously elucidated. In this study we investigated the diploid chromosome number and performed karyotype and fluorescence in situ hybridization (FISH) analyses of the telomere sequence on chromosomes of T. cornutus. A diploid chromosome number of 36 was identified in larval somatic cells, and the karyotype comprised 16 pairs of metacentric and 2 pairs of metacentric/submetacentric chromosomes. In the telomere FISH analysis using a vertebrate telomere probe, fluorescein isothiocyanate-positive hybridization signals were clearly observed on the telomeric regions of the chromosomes. This result suggests that the FISH technique is appropriate for other Turbinidae species and that the telomere sequence of T. cornutus is (TTAGGG)n, which is the same as that of vertebrates.