In the previous number of this Journal, the Rev. E. O’Meara has charged me with carelessness, and thinks if I had read his papers with greater attention I should have expressed my doubts of the genuineness of his new species more cautiously. I have, therefore, read them again, in order to apologise for any misrepresentation, and correct any errors. I find two or three mistakes; viz., Cocconeis divergens should have been C. clavigera, the remarks on Navicula pellucida ought to have preceded the passage quoted by the Rev. E. O’Meara. I have also inadvertently made him the author of Raphoneis liburnica, whereas he is only responsible for the variety. With these exceptions, I really find nothing to retract. At page 91, the Rev. E. O’Meara says : “How inapplicable are some of Mr. Kitton’s observations on dredging to the forms found by me in the dredgings from Arran.” I find, on referring to his first paper, he says, “this material was procured from depths varying from ten to thirty fathoms,” &c. I do not think, therefore, I was unjustified in assuming that his material was similar to others procured from like depths, and which, in almost every case, consist of sand, animal and vegetable debris, and valves of diatoms. My copy of the ‘Microscopical Journal ‘in which his first paper appears has no description of the figures. I therefore assumed that the figures were magnified 600 diameters, as that was the degree of amplification more frequently used in the second paper. I do not find the number of diameters stated in the text. If the Rev. E. O’Meara refers to the text of his first paper, he will find Navicula pellucida is fig. 2 ; and fig. 2 in the plate is the form which, I think, resembles Navicula pandura much too elosely to entitle it to rank as a new species*. N. denticutala is fig. 3 in text. I am still unconvinced of the specific distinctness of Surirella pulchra and S. gracilis, or that they differ sufficiently from?. lata to warrant their separation from that species. I am willing to admit that a remarkable difference exists between the figures of S. pulchra and S. gracilis; viz., the crenulate margin ; alæ are also wanting, but as these differences are not noticed in the text, I am inclined to doubt the correctness of the figures, and suppose the crenulations represent the undulations of the alæ, and that the margin of the valve is not shown in the figure.