466 PHTSOSTOMI. 



the oill-opening. Teeth — those on the palate with globular heads, in large semi-ovate patches : considerable 

 variation in size and direction of these patches of teeth exists, as it not unfrequently happens that some are 

 wanting. Fins — dorsal rather higher than the body, the spine of moderate strength, anteriorly serrated in its 

 upper, rough in its lower half, posteriorly serrated, it is as long as the postorbital portion of the head : length 

 of the base of the adipose dorsal 2/3 of that of the rayed fin. Pectoral reaches two-thirds of the distance to 

 the ventral, its spine is rather stronger than that of the dorsal which it equals in length, externallj' it is 

 serrated, internally denticulated. Ventral does not extend so far as the anal. Upper caudal lobe the longer. 

 Colours — purplish superiorly, becoming dull white beneath, fins externally stained with gray or black, and a 

 blackish spot on the adipose dorsal. Air-vessel — Taylor described the air-vessel of Gagata tijpus as that of Arius 

 gagora : Owen appears to have followed him, and (Comp. Anat. i, p. 491) observes that amongst fishes this organ 

 is " seldom divided lengthways into two halves as in Aritts gagora." . . . . " The divided air-bladder of the .... 

 Arius gagora, in which the divisions are confined to the forepai-t of the abdomen and are enclosed in osseous cups 

 developed from the anterior trunk vertebra." (See Gagata typus, Bleeker). I have found it in this species as 

 follows : large and somewhat heart-shaped. On removing its lower wall a longitudinal septum is seen in its 

 posterior half but does not exist anteriorly. It has three transverse subdivisions, forming it into five cliambers, 

 the anterior of which is nearly half the size of the entire organ, it having no longitudinal septum. The four 

 lateral chambers communicate freely with one another on either side, also antei'iorly with the large chamber. 



Habitat. — Seas, estuaries and tidal rivers of Orissa and Bengal to Siam. It attains H feet (or according 

 to Hamilton Buchanan 3 feet) or more in length : it is commonly seen about 8 or 10 inches long. The 

 specimen figured (10 inches long) was from Calcutta. 



20. Arius jatius, Plate CVI, fig. 4. 



Pimelodus jatius, Ham. Buch. Fish. Ganges, pp. 171, 376; Bleeker, Beng. en Hind. p. 58. 

 Arius jatius, Blyth, Proc. As. Soc. Beng. 1860, p. 151. 

 Nga-youn and Nga-yeh, Burmese. 



B. vi, D. i I 0, P. 1/10, V. 6, A. 18 (-fy), C 17. 



Length of head 4j, of caudal 5, height of body 5|- in the total length. Eyes — diameter 4i to 5 in the 

 length of head, li diameters from the end of snout, and If to 2 apart. Height of head nearly equals 

 its width, the latter equals its length excluding the snout. Upper jaw the longer : the extent of the gape of 

 the mouth equals one-third of the length of the head. Summit of the posterior portion of the head sparingly 

 granulated, the occipital process more thickly so. The median longitudinal groove on the head narrow, 

 and continued almost to the base of the occipital process, which latter is keeled, as wide at its base as long, and 

 reaches the narrow V-shaped basal bone of the dorsal fin. Opei-cle wider than liigh. Barbels — short, 

 the maxillary pair shoi-ter than the head, the outer mandibular pair just reach the gill-opening. Teeth — 

 villiform, in a band six times as long as wide in the premaxillaries : on the palate globular, in a small oval patch 

 posteriorly, scarcely exceeding half the diameter of the eye ; they may be entirely absent. Fins — dorsal as 

 liigh as the body, its spine strong, as long as the head excluding the snout, serrated on both sides : 

 the base of the adipose dorsal 4,5 of that of the rayed fin. Pectoral spine as long as that of the dorsal, serrated 

 externally, denticulated internally, it reaches as far as the ventral tin and the latter the anal. Colours — of a 

 dark bluish along the back, becoming lighter on the sides and beneath. Pins yellowish, lower half of dorsal 

 stained with gray. Upper edge deep black. A deep black spot on the upper half of the adipose fin, caudal 

 edged with black, and anal with a dark spot on its edge near the middle. 



This fish is very closely allied to A. gagora, but it has lai'ger eyes, &c. The sjiccimen figured has no 

 teeth whatever on the palate and is an Hemipimelodus, but having closely compared it with four more 

 specimens having teeth as described, I feel convinced of their identity. 



Habitat. — Estuaries and rivers of Bengal and Burma, ascending far above tidal reach. It attains a foot 

 or more in length. 



21. Arius tenuispinis, Plate CVII, fig. 5 (head). 



? Arius Layardi, Giinther, Ann. and Mag. Nat. Hist. 1866, p. 473, pi. xv. 



B. vi, D. I I 0, P. 1/10, V. 6, A. 18 (Jj), C. 17. 



Length of head 3-^, of caudal 4-», height of body 5^ in the total length. Fyes — diameter 7 in the length 

 of head, 2| diameters from end of snout, and 3? apart. The greatest width of the head equals its length 

 f xcluding the snout. Th<? extent of the gape of the mouth equals one-third of the length of the head. Median 

 hmgitudinal groove on the head narrow, and does not quite reach the base of the occipital process, 

 which has a slight keel, is a little longer than wide at its base, and rather convex posteriorly where it reaches 

 a narrow and V-shaped basal bone of the dorsal fin. A few granulations on the top of the head, also along the 

 middle of the occipital process. Barbels — the maxillary ones reach the end of the head, the outer mandibular 

 ones are 1/3 shorter. Teeth — none on the palate. Fins — dorsal spine very weak and thin, nearly as long as 

 the head excluding the snout, serrated posteriorly : base of the adipose equals half that of the rayed 

 dorsal fin. Pectoral spine as long as the dorsal, but slightly sti-onger, roughened externally, serrated internally. 

 Caudal forked. Colours — silvery along the back, becoming lighter on the sides and beneath. 



