242 Dr. Hancock on some species of Fishes and Reptiles 



Doras costata. 



Dor. brunnescenti-grisea, laminis lateralibus circiter 27. 



D., 1 0. P., 4-. v., 7. A., 9. C, 20. 



This species has six cirri at the mouth. The head is depressed ; the 

 whole body mailed, excepting at the abdomen^ with strong bony costi- 

 form plates in a single longitudinal series, in the centre of which appears 

 a single row of spines, curved backwards, and extending from the head 

 helmet to the root of the tail. The abdomen is flat, and destitute of bony 

 plates. A large and remarkably strong bony arm constitutes the first ray 

 of each pectoral fin. This arm is strongly serrated on both its anterior 

 and posterior edge. The mouth is small ; the opercula of the gills small 

 and close, requiring dissection to examine the gill membrane, which con- 

 sists, as I have before observed, of four rays ; the first ray of the anterior 

 dorsal fin is a strong serrated spine. The posterior dorsal fin is small and 

 fleshy without rays. This fish frequents only the fresh water of pools, lakes, 

 and rivers, lives by suction, and on aquatic insects, and grows to about 

 a foot in length. The colour of the body inclines to brovmish gray. If 

 has no proper teeth, but the lips are beset with minute sharp points. 



This species is one of those fishes which possess the singular property 

 of deserting the water, and travelling over land. In those terrestrial ex- 

 cursions large droves of the species are frequently met with during very 

 dry seasons, for it is only at such periods that they are compelled to this 

 dangerous march, which exposes them as a prey to so many and such 

 various enemies. When the water is leaving the pools in which they 

 commonly reside, the Yarrows, (a species of Esox, Linn.,) as well as 

 the second species of Hassar, to which I shall presently refer, bury them- 

 selves in the mud, while all the other fishes perish for want of their na- 

 tural element, or are picked up by rapacious birds, &c. The flat-head 

 Hassars, on the contrary, simultaneously quit the place, and march over 

 land* in search of water, traveUing for a whole night, as is asserted by the 



grs. each. They, consist of two pearly bones, which are loose in the cavity of the 

 skull, and without any attachment whatever, each being inclosed in a thin and 

 very delicate tunic, which lies in contact with the brain. 



* In an excursion made by my friend, Mr. Campbell, of Sparta Estate, 

 Essequibo, with his family to the Sand Reefs, a spot situated about six mile* 



