THE FISH. 7 



has moreover some evident analogies, which we will 

 proceed to detail. It is divided into three orders : 



Cyclostomata, in which the jaws are united into 

 an immoveable ring, and the gills open by numerous 

 holes. 



Selachii have the gills of the preceding, but not 

 their jaws. 



Sturiones have the gills open in the ordinary man- 

 ner of fish, by a single cleft furnished with an oper- 

 culum or gill cover. 



The other series, or that of the common fish, pre- 

 sent to me at first a primary division of those in which 

 the maxillary bone, and the palatine arch, are inserted 

 in the cranium. Of these I make the order plegtog- 

 nathi, divided into two families, gymnodontes and 

 sclerodermoid. 



Next, I find fish with perfect jaws, and with gills 

 not in the shape of a comb, as is usual, but with a 

 series of small tufts. Of these I also form the order, 

 which I name lophobranchii, and which includes only 

 a single family. 



Still there remains a very large number of fish to 

 which no other characters can be applied than those 

 of the exterior organs of locomotion. After a long 

 series of researches, I find that the least objectionable 

 of such characters are those used by Ray and Artedi, 

 derived from the nature of the first rays of the dorsal 

 and anal fins. The common fish may thus be divided 

 into malacopterygii, in which all the rays are soft, 

 except occasionally the first of the dorsal or pectoral 



