The above paper on the Plymouth gobies (p. 48) was finished and in print before the new work of C. G. J. Petersen (“Beretning til Land brugsministeriet fra den danske biologiske Station,” XXVI, 1919) came to hand. Although a second description and differentiation of the common forms is now unnecessary after his accurate and detailed account of them, yet as a corroboration of his identifications and as a record of the occurrence and distribution of the young gobies to be found at Plymouth (three of which are not described by Petersen), it seems advisable to keep the whole of my work intact, although in some measure it contains a repetition of the conclusions arrived at by him. I have therefore altered nothing, except adding the words “up to 14 mm.” with regard to Gobius pictus in the table, p. 79, and merely confine myself to a few notes in this appendix with regard to any slight differences between his specimens and those from Plymouth. The three species not described by Petersen, namely Gobius elongatus, Gobius Jeffreysii and Gobius paganellus are apparently, with the exception of Gobius Jeffreysii, not present at all in the Danish waters. On reading his conclusions as to the specific value of the number of vertebræ and fin rays I feel still more strongly that the form hitherto known as the deep water form of Gobius minutus, and which I have here distinguished as Gobius elongatus, is a true species, although closely related to Gobius minutus.