Bivalves play an important role in the ecosystems they inhabit and represent an important food source all over the world. So far limited genetic research has focused on this group of animals largely due to the lack of sufficient genetic or genomic resources. In this study, we performed de novo transcriptome sequencing of Zhikong scallop (Chlamys farreri) using the 454 GS FLX platform. A library representing diverse life stages and adult tissues of C. farreri was sequenced to identify groups of genes involved in a broad range of biological processes.Based on this resource, we performed the first large-scale transcriptome comparison between the two scallop species, C. farreri and P. yessoensis, and identified a number of putative fast-evolving genes, which may play an important role in scallop speciation and/or local adaptation.A large set of single nucleotide polymorphisms and simple sequence repeats were identified, which are ready for downstream marker development. This transcriptomic resource should lay an important foundation for future genetic or genomic studies on C. farreri.