The basis for Mr. Hallam' rejection of the hypothesis on the evolution of Liostrea into Gryphaea is briefly examined and is shown to be inadequate. For Liostrea real evidence is lacking. For Gryphaea the evidence, though copious, is unsound for it is based upon an improper treatement of his collections. Moreover, the features he measures are not sufficiently significant and the reader is left in considerable doubt as to the actual range of his measurements. His aspersion upon previous workers in this field is entirely unjustified.