These notes are intended to form an appendix to the author's paper on the anatomy and classification of the Heteropoda, read before the Society last session. He finds the relationship between Firola and Firoloides even closer than he had supposed, and that, with the exception of gills in the former genus, nearly every anatomical point occurring in one, may be distinctly traced out in the other, only differing in relative characters. The author describes in detail the anatomy of Firola, illustrating his description by a drawing.