All heptoses produce with orcinol in dilute HCl two characteristic colored compounds which differ greatly in their absorption spectra. Three different modifications of this reaction were found useful. Procedure i--To 2 cc. of a solution containing 20 to 100 y per cc. of ketoheptose or 5 times as much of an aldoheptose is added 0.4 cc. of concentrated HCl, sp. gr. 1.19, in a test-tube with a gro...

Identifying isolated teeth of fossil selachians only based on qualitative characters is sometimes hindered by similarity in their morphology, resulting often in heated taxonomic debates. On the other hand, the use of quantitative characters (i.e. measurements) has been often neglected or underestimated in characterization and identification of fossil teeth of selachians. Here we show that, empl...