In this paper we present the Scali ShMem - ScaShMem - library, a compatibility library for Cray SHMEM. SHMEM is a popular application programmers interface for MPP (Massive Parallel Processor) programming, but has previously been limited to MPPs from Cray Inc. and SGI Inc. ScaShMem is layered on top of Scali’s MPI implementation; ScaMPI, using multiple threads enabled by ScaMPI’s thread-hot & -safe features. Since ScaShMem is layered on top of MPI, one-sided communication of SHMEM can be mixed with MPI message passing. Near native Scali MPI performance is demonstrated for ScaShMem, justifying porting SHMEM applications to a price favorable cluster environment.