April 19, 1908. Sunday. Past the morning at the U.S.N.M. with Bassler. Looked over the thin sections of Brach. shells and found that all Cambrian brachiopods had a non-fibrous, granular, exceeding fine punctate structure. These punctae are arranged in lines, closely adjacent and seem to me not to be continuous pores, but interstitial pores passing from layer to layer. As one works the focusing screw of the microscope the upper ones extinguish and lower ones come into view. Not a single Cambrian brach-iopod has the fibrous, distinctly punctate shell structure seen in Middle Ordovician forms. Bassler thinks he sees a shell structure in the early Pentamerus that is identical with the true Pentam-eris of the Silurian. In the field there is a distinct study to be made that will yield good results. It should begin with recent shells and continue through all time into the basal Cambrian. It only adds 1 value in a general classification of brachs, but it is of distinct value in generic work and in the Cambrian era of much greater value.