1. J. D. Taylor, W. J. Kennedy andA. Hall,Bull. Brit. Mus. Nat. Hist. (Zool.) Suppl. 3 (1969) 1.
2. Idem, ibid 22 (1973) 253.
3. O. B. Bøggild,K. danske Vidensk. Selsk. Skr. 2 (1930) 232.
4. A. J. Kohn andA. C. Riggs,Syst. Zool. 24 (1975) 346.
5. L. R. Cox, in: ?Treatise on Invertebrate Paleontology?, edited by R.C. Moore (University of Kansas Press, 1960)I p. 84.