■of a neiv Genus of Fish named Pul/joiera. 39 



TOinates in a point : the fin which borders it below and 

 -above is however rounded at its extr(-nlit^' : the radii arc 

 subdivided in proportion as thev recede from their origin ; 

 Jhose of the pectoral and ventral fins have a resemblance to 

 them, except in the difference of their height. They are 

 all so close to each other that thev do not seem to be suscep- 

 tible of motion. 



III. Of' the Head. — The branchial aperture is of consi- 

 derable size, which is never the case in other fishes, unless 

 the number of the branchio-stege radii increase in propor- 

 tion. But in the lic/iir thcj'c are none : they would indeed 

 be almost useless, siuce the branchio-stege membrane, in- 

 stead of being so thin as to fold up or expand at pleasure, 

 consists of a thick skin. As it is of suflicient extent to ex- 

 ceed a good deal the opposite edge of the branchial aper- 

 ture, it is supported towards the middle by a long osseous 

 plate. 



It may readily be imagined that a branchio-stege mem- 

 l)rane, like the present, cannot perform the functions which 

 it is known to perform in other fishes, if the arrangement 

 of the plates which cover the head did not compensate for 

 this deficiency by a supplementary organization, which 

 brings all these parts into perfect agreement. 



The middle of the head is protected by a large plate, 

 composed of six pieces all articulated together. This kind 

 of helmet is separated from the operculum by a band com- 

 posed of small square pieces, w hich coming from the eye 

 proceed obliqueiy on the nape of the neck. About the 

 middle it is observed that two of these pieces adhere by a 

 jiiembrane only to the first piece of the operculum, while 

 their opposite edge is free. As this fissure communicates 

 with the cavitv of the mouth, the water conveyed into 

 the branehias is sti-ongly compressed both by the pieces of 

 the operculum, and by the long plate which supplies the 

 place of the branchio-stege radii : this liquid raises up the 

 two small moveiible pieces, and opens a passage through 

 which it escapes as through a valve. 



The operculum exhibits nothing remarkable : it is com^ 

 posed of three pieces ; the anterior and posterior are nearly 

 ■of the same size ; the third, which is situated between the 

 two, is much smaller, and has the form of an equilateral 

 triangle : above this third piece the two others arc contigu-^ 

 ous. The leaves of the branchia; arc single. 



The form of the head approaches near to that ol the esocc;: 

 it is lonti and flat from ihc top downwarcb, and the mferior 

 jaw projects a little forwards. 



C 4 The 



