I.—What is a Brachiopod?1

^{page 145 note 2} Plates IX. and X. will accompany Part II.

^{page 146 note 1} A very remarkable paper by M. de Lamanon, “Sur les Térébratules ou Poulettes, et déscription d'une espece trouvée dans les mers de la Tartarie Orientale,” was published in 1797 in vol. iv. of the Voyage de la Pérouse autour du monde. In this memoir, which appears to have been overlooked by all those who have treated of the same subject, the author describes as far as his knowledge permits the soft parts of the animal of a species of Terebratella.

^{page 148 note 1} In a very interesting paper on the development of the loop in Wald. cranium and W. septigera entitled “Bidrag til Vestlandets Molluskfauna,” published in the “Saerskilt Aftryk af Videnskabsselskabets Forhandlinger” for 1875, Mr. Herman Friele has started the hypothesis that the loop becomes modified with age, and he indicates a most remarkable development of a simple loop out of a compound one, but before this important question can be definitely settled a complete connecting series of the different ages of a same species will have to be examined, which has not been hitherto done to my entire satisfaction.

^{page 150 note 1} Philosophical Transactions Royal Society, vol. 148, 1858.

^{page 150 note 2} Sux l'animal des Lingules, Bull. Soc. Philomatique de Paris, vol. i., 1797, and Sur l'animal de la Liagule anatina, Mémoirs du Museum, vol. i., 1802.

^{page 150 note 3} Transactions of Zool. Soc, vol. i., 1833, and Davidson's General Introduction to British Fossil Brachiopoda, vol. i., 1853.

^{page 150 note 4} Annals and Mag of Nat. History, vol. xiv., 2nd series, 1854.

^{page 150 note 5} Journal de Conehyliologie, 1857, 1859, and 1860.

^{page 150 note 6} Anatomie der Lingula anatina, 1845.

^{page 150 note 7} On the Physiology of the Pallial sinuses of the Brachiopoda, Transactions of the Linnæan Society of London, vol. xxiii., p. 373, 1862.

^{page 150 note 8} An instructive note on the primary divisions of the Brachiopods by T. Gill will be found in the Annals and Mag. of Natural History, 4th, series, vol. xii., 1873.

^{page 151 note 1} Recherches'sur l'organisation du Manteau chez les Brachiopodes articules, Caen, 1864, and to which the reader is referred for further details.

¹ This memoir is the substance of a lecture delivered by the author to the Brighton and Sussex Natural History Society on the 11th of February, 1875, and subsequently published in French with additions and plates in vol. x. of the Annales de la Société Malacologique de Belgique for 1876.