The Collaborative International Dictionary of English v.0.48:

Muschelkalk \Musch"el*kalk`\, n. [G., from muschel shell + kalk
   limestone.] (Geol.)
   A kind of shell limestone, whose strata form the middle one
   of the three divisions of the Triassic formation in Germany.
   See Chart, under Geology.
   [1913 Webster]