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Show 794 MR. F. DAY ON THE FISHES OF YARKAND. [Dec. 5, partially free in the abdomen, as is seen in genus Botia. But granting Kessler's description to be accurate, I cannot think that such a fact alone would justify instituting a new genus for the reception of his species. The reason for air-vessels being enclosed in bone in some fishes is very obscure ; and I sometime since adverted, in the ' Proceedings ' of this Society, to the circumstance of such not being infrequent in Indian Silurida. I found amongst the Indian genera of Siluroids of the fresh waters, or those which entered fresh waters, as follows : - A. Air-vessel free in the abdominal cavity. 1. Rita; 2. Erethistes; 3. Pseudeutropius; 4. Silurus; 5. Olyra; 6. Macrones; 7. Callichrous; 8. Wallago; 9. Arius; 10. Hemipimelodus*; 11. Osteogeniosus; 12. Batrachocephalus; 13. Panga-sius; 14. Plotosus. Of these, five (no. 9, 10, 11, 12, and 14) are marine forms, entering fresh waters for predaceous purposes. B. Air-vessel more or less enclosed in bone. 1. Ailia; 2. Ailiichthys ; 3. Sisor ; 4. Bag arius ; 5. Amblyceps; 6. Saccobranchus; 7- Silundia; 8. Eutropiichthys; 9. Gagata; 10. Pseudecheneis ; 11. Exostoma; 12. Clarias; 13. Glyptoster-num. All of these are freshwater genera. Thus the necessity for the air-vessel being enclosed in bone appears to be restricted to the fishes of fresh waters of the plains or hills. These thirteen freshwater genera having the air-vessel enclosed in bone are divisible as follows :- 1. Waters of plains. a. Large rivers: no suckers on the chest. Ailia, Ailiichthys, Sisor, Bagarius, Silundia, Eutropiichthys, Gagata. /3. Large rivers: descending to the sea. An accessory air-breathing apparatus. Clarias. y. Smaller rivers, tanks, &c. An accessory air-breathing sac. Saccobranchus. 2. Waters of the plains or hills. No sucker on chest. Amblyceps. Sucker on chest. Glyptosternum. 3. Waters of hills. Sucker on chest. Pseudecheneis. Chest adhesive. Exostoma. * I erroneously gave the air-vessel as enclosed in bone in Hemipimelodus. The genus was defined by Bleeker; and it was suggested that Pimelodus cenia, H. B., was an example. Not having an estuary or marine species, as H. jatius, by me, I took P. cenia, H. B., as one of the genus; whereas I now find that it belongs to Gagata, which embraces P. cenia, P. viridescens, P. itchkeea, and two or three other species. Pimelodus jatius, H. B., has no palatine teeth, as stated in the ' Fishes of the Gauges;' it is a Hemipimelodus, Bleeker; and of it I possess specimens from the Hooghly ; but I consider such as probably only a variety of Arius. |