06 ACANTHOPTERTGII. 



the first anal spine is very short, the general colour is steel blue with a golden lateral band tvro scales wide : 

 the caudal lobes are of equal length. 



Bleeker observes that Casio chrijsozona is closely allied to 0. cmrulaureus, but the body is more elongated 

 in tlie former than in the latter. The temporal band of scales is largest in the C. ccerulaureus, which has its 

 golden lateral band above instead of below the lateral line. 



Habitat.— Hed Sea, seas of India. 



Eighth group — Gerrina. 



Branchiostegals six. Body elevated or oblong. Preopercle serrated or entire. Mouth very protractile. 

 Villiform teeth in the jaws. A single dorsal fin : three anal spines. Air-vessel simple. 



Genus, 28 — Datxioides, Bleeker. 

 Branchiostegals six: pseudobranchire. Body elevated. Ei/es of wcoderate size. Premaxillaries very protractile. 

 Breopercle serrated. Villiform teeth in the jaivs untJwut canines; vomer, palate, and tongue edenttiloiis. A single 

 dorsal fin having twelve stout splines : anal ivith three : caudal rounded. Scales ctenoid. Air-vessel simple. Pyloric 

 appendages few. 



Geographical distrihution. — ]\Iouths of large rivers from the Hooghly throughout Burma to the Malay 

 Archipelago. Rarely found beyond tidal reach although it frequently ascends into fi-esh water. 



SYNOPSIS OF INDIVIDUAL SPECIES. 

 1. Batnioides pjolota, D. tj-x^, A. -^^.^, L. 1. 48. Brown with several cross bands. Estuaries of the 

 Ganges to the Malay Archipelago. 



1. Datnioides polota, Plate XXIV, fig. G. 



Coins polota. Ham. Buch. pp. 95, 370, pi. 38, f. 31 ; Temm. and Schleg. Fauna Japon. Poiss. p. 17 ; 

 Richards. Ich. Sulphur, p. 83. 



Coi^Ls binotatus, Gray and Hard. Ind. Zool. ; Temm. and Schel. 1. c. p. 17 ; Richards. 1. c. p. 83. 



Datnia polota, Cantor, Catal. p. 16. 



Lobotes hexagona, Bleeker, Nat. Tyds. Ned. Ind. i, p. 9, and ii, p. 165. 



Batyiioides polota, Bleeker, 1. c. v, p. 441, and Atl. Ich. Perc. t. xxvii, f. 1 ; Giinther, Catal. i, p. 339. 



Nya-hya and Nga-ivet-ma, Burm. ; Nga-pree-gryn and Nga-thaJc-hoiv, Arrac. 



B. vi, D. Ti-H, P. 19, V. 1/5, A. J^, C. 17, L. 1. 48, L. r. if, L. tr. 12/25, Cffic. pyl. 5. 



Length of head 2/7 to 1/3, of caudal 2/11 to 1/6, height of body 2/5 to 1/3 of the total length. Eyes— 

 diameter 1/5 of length of head, l-i- diameters from end of snout, and 1 apart. The posterior processes of the 

 premaxiUaries reach to behind the orbit. The maxilla extends to below the middle of the orbit. Preopercle 

 seiTated along both limbs : both shoulder-bone and the one in the axilla serrated. Teeth — fine in the jaws, 

 with the outer row sHghtly enlarged. Fins — dorsal spines strong, every alternate one being thickened on one 

 side, the fifth and sixth the longest and equal to two-fifths of the height of the body or half of the length of 

 the head : second anal spine the strongest and longest, equalling the highest in the dorsal fin : caudal rounded. 

 Colours — brownish, glossed with copper, having six or seven narrow brown vertical bands on the body and 

 similar ones radiating fi-om the orbit. 



Habitat. — Estuaries and within tidal influence of the Ganges and rivers of Burma to the ]\Ialay 

 Archipelago, attaining at least 1 foot in length : though not esteemed as food it is eaten by the poorer classes. 

 The specimen figui-ed (6j inches in length) is from Calcutta. 



Genus, 29 — Gerres, Cuv. 

 Biapterus, Ranz. : Chanda, sp. Ham. Buch. : Gatochcenum, Cantor : Synistius, Gill : Euciiiostomus, Baird, Gir. 



Branchiostegals six : pseudobraiichice. Body elevated or oblong, and compressed. Mouth very protractile and 

 descending when produced. Preopercle as a rule entire, rarely serrated. Eyes comparatively large. Villiform 

 teeth in the jaws. Inferior piharyngeal hones firmly united by a suture. Length of the bases of the spinous atul soft 

 portions of the dorsal fin of nearly equal extent, and having a scaly sheath into which it can be wholly or partially 

 received : the spines numbering nine or ten, the rays ten or eleven : anal ivith three spines : caudal forked. Scales of 

 moderate size, when ctenoid very slightly so. Air-vessel simple. Pyloric appendages feio. 



Gill places the Gerrini as a distinct family. 



Geographical distribution. — All the tropical seas, entering estuaries. Some apparently being mostly 

 confined to the latter situations, and ascending into brackish or fresh waters as high as tidal influence extends. 



Uses. — As food these fishes are mostly eaten by the indigent classes, being little esteemed whilst fresh 

 on account of their numerous bones and deficiency in flavour. As they salt and diy well, large numbers are 

 extensively prepared in this manner for future use or as a matter of export trade. 



The species comprising this genus are somewhat dilEcult of determination unless a good collection is 

 brought together, but even then some important considerations have to be borne in mind prior to deciding 

 whether the specimen belongs to a known or an unknown species. The eye, certainly in some, increases in 



