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Show 187L] SURGEON F. DAY ON INDIAN SILUROID FISHES. 287 commented upon the air-vessel of the Gagata typus, Bleeker; it then occurred to me how few inquiries appeared to have been instituted respecting this matter amongst the Siluroid fishes of India, and that what had been made referred chiefly to the genera Clarias, Plotosus, Saccobranchus, Wallago, Callichrous, and Arius. Genus EUTROPIICHTHYS. In the E. vacha, Ham. Buch., the air-vessel is in the form of a tube rather enlarged at either extremity, its diameter being equal to about one-half of that of the vertebral column posterior to it. It closely embraces the body of the third vertebra, lying across it and the large vessels. It then curves backwards and upwards, in the first portion of which course it is slightly protected by a projection on the body of the second vertebra. In the last portion of its extent it is protected by a wide concave expansion of the lateral processes of the first and second vertebrae. This expanded portion of the vertebrae, in which the air-vessel lies, is about equal in width to that of the body of a vertebra. Genus AILIA. In the A. bengaliensis, Gray & Hard., the air-vessel is of the same description as in the E. vacha, with the exception that it is rather more dilated at either extremity. I would here remark upon a curious specimen of this species, 6| inches long, which I procured at Delhi. It has more or less distinct spines along the whole course of its back, most prominent midway between the eye and the base of the caudal fin. Genus PSEUDEUTROPIUS. In the P. garua, Ham. Buch., the air-vessel is contained in the abdominal cavity, but is small, somewhat heart-shaped, with a short prolongation on either side anteriorly. It is firmly attached to the anterior vertebrae, embracing their bodies, and being a little extended laterally on either side. Genus PANGASIUS. In the P. buchanani, Cuv. & Val., the air-vessel is contained in the abdominal cavity; it extends from opposite the base of the pectoral fin to as far as the end of the anal. A slight contraction exists between its anterior third and the remainder of the organ. Genus SILUNDIA. In the S. gangetica, Cuv. & Val., the air-vessel is also contained in the abdominal cavity. It is large, and with very thin walls. Genus MACRONES. In the M. cavasius, Ham. Buch., the air-vessel is contained in the abdominal cavity, but not loosely as in the Pangasius. It is of a |