THE largest known species of Enteropneusta was discovered by Fritz Muller on the Brazilian coast, at a place named Armacao da Piedade, in the State of Santa Catarina. Fritz Muller's notes in which he describes the animal were fortunately collected and published in the year 18981 by Dr. Hermann von Ihering, former director of the Museu Paulista of Sao Paulo. In those notes (p. 36), Fr. Muller said that he caught many tornaria larvae from 1860 onwards in the plankton off the same beach. The first Balanoglossus was captured in 1884, and in the following year many others were caught. The extraordinary size of the animals (1.5 m. in length) justified the name Balanoglossus gigas. Some of the specimens were sent to Spengel2, who gave them in 1893 a new description and re-named them Ptychodera gigas. In a later monograph on the Hemichordata, recently published, van der Horst3 re-described the same animal under the name of Balanoglossus gigas Fr. Muller.