IT has been observed1 that the formation of enamel in a small tooth germ of the crossopterygian, Latimeria chalumnae, is external to the dentine, and examination of more material has confirmed this impression. Serial sections through developing teeth, which had been stained as indicated in Table 1, showed quite clearly that the enamel matrix develops externally to the dentine (Fig. 1), and not as a change in the outer layer of the dentine that has already formed, as has been reported in actinopterygians by Kerr2 and in some larval and adult amphibians2,3.