presented to the Zoological Society. 241 



more of a scientific form. At present you must be content with a few 

 extracts from my notes, written during my residence in the colony, which 

 relate to some of the animals, whose characters and habits appeared ta 

 you and some other members of the Society, while we were looking over 

 the collection, to possess most novelty and interest. 



We appear to have in Demerara several nondescript fishes belonging 

 to the nearly allied genera, Silurus2.ViA Lorioaria^ Linn. Among these are 

 two species, specimens of which are in your Museum, belonging to that 

 division of the former genus, which by their mailed or plated covering 

 approach most closely to Loricaria, 



These species are distinguished by the negroes under the titles of the 

 Flat'head and Round-head; and are also called Que Que, from the noise 

 they make when taken out of the water, which much resembles the cry 

 of a rat. They are the Hassar of the Arowaks. 



Tlie first of these, or the Flat-head Hassar, is a species of Doras, La- 

 cep., closely allied to the typical one, the Silurus coUatus, Linn.; from 

 the figure of which, as given by Bloch, it differs chiefly by the tail not 

 being so deeply forked. The fishes of this group appear, however, to 

 resemble each other so nearly, as to render it unadvisable to characterize 

 the present as new, without possessing the opportunity of comparing it 

 with other and numerous specimens. I shall therefore content myself, 

 for the present, with describing it, premising only that the number of 

 large plates one ach side is twenty-seven, while, according to Lacepede, 

 in the Doras costatus it is about thirty-four. The same author also 

 states, that the rays of the branchiostegous membrane are five, while I 

 have never been able to detect more than four in my species.* 



* The paucity of rays in this organ is a curious circumstance generally ob- 

 servable in the fish of South America. I have never met with any one with more 

 than five rays in the gill membrane. Another singular anomaly remains to be 

 noticed in the fish of the Tropics, viz. the large brain-bones, which in northern 

 latitudes are either wanting, or are so small as to have escaped common obser- 

 vation. They appear, indeed, to be without a name, or entirely unnoticed by 

 naturalists, as far as I know. 



Specimens of these bones have been presented to the Zoological Society to shew 

 the developement of this character. In the Siluri they are remarkably conspicu- 

 ous. In the species called Gilbagrt they weigh, in the full-grown fish, about 20 



