Whilst engaged on the new Geological Survey in the neighbourhood of Mariow, I had the good fortune to come across an exposure of Chalk Rock yielding an exceptionally rich fauna, including a single specimen of an ammonite which appeared to be new to science. This ammonite was therefore shown to Dr. Kitchin, Mr. Crick, Dr. Rowe, and Mr. H. Woods, none of whom had seen the species before or could recognize it as a form already described. The discovery of new Cephalopods from the Chalk is now so rare that it seems worth while to draw attention to this, although the whole of the accompanying fossils have not yet been identified.