Saukoids.- 



-FISIIES.- 



-Lepidostids. 



IGl 



fit, and to attain the weight of one thousand pounds, 

 so as to require a yoke of oxen to draw it out of the 

 river. Neitlier tlie descriptions of Greek nor of Roman 

 authors enable us to ascertain the species to wliich tliey 

 gave the names oi Acipenscr, Atlihis, or Helops. Tlie 

 second of these appellations is preserved in the Italian 

 Adila applied to the Acipcnser sturio of the Adriatic, 

 called by the Germans Slor, a word having reference 

 (Ileckel says) to the turning and grovelling habits of 

 the fish (walloping). Our English word Sturgeon and 

 tlie French Etiirgeon have evidently come from the 

 Northmen or Eastraen. There is reason to believe 

 that the common English Sturgeon is diftorcnt from 

 the Slui-io of the Mediterranean, and of the rivers of 

 eastern Germany, though they have generally been 

 considered to be the same species. 



Tlio Sturgeon is denominated "a royal fish" in Eng- 

 lish acts of parliament. In the time of Edward I. 

 it was declared that the whole Sturgeon belonged to 

 the king in virtue of his royal privilege ; but of the 

 Whale, the head only belonged to the king, and the tail 

 to the queen, the captors retaining the carcass.* In 

 tlie reign of Edward II. the statute about Sturgeons 

 was amended so as to exclude all purchased Sturgeons 

 and others not taken in the sea. 



As the Sturgeon family are acknowledged represen- 

 tatives of the Ganoids, it may be advantageous to the 

 student if we advert to a few peculiarities of structure, 

 in explanation of the technical characters of the order 

 mentioned above. 



In the brains of fishes there is a pair of nearly globu- 

 lar protuberances, generally very conspicuous and easily 

 I'ecognizcd as being the second division of the organ, in 

 proceeding from before backwards. They furnish the 

 nerves of sight, and are named optic lobes. In osseous 

 fishes the fibres of these lobes hitermix and decussate 

 on the mesial line ; but in the Sturgeons this decussa- 

 tion does not take place. In them also the arterial 

 stem, or fourth chamber of the heart, is provided with 

 two rows of valves at its origin in the ventricle, and 

 one row at its distal end. There are five movable bran- 

 chial arches, with interior denticulated rakers. The 

 gills are pectinated and free at the tips. In the Stur- 

 geons, moreover, there is an accessory gill attached to 

 the inner face of the operculum ; and near it a pseudo- 



brancbia, which receives arterial blood that has already 

 undergone the process of respiration, and transmits it 

 to the eye. The five passages between the branchial 

 arches unite in the common external gill-opening of 

 each side, which is covered by the operculum. All the 

 Sturionidans have not the same arrangement of the 

 accessory gills and psoudobranchise, since in the Scapld- 

 ri/hnc/ius the former of these organs is present, but 

 the latter is absent ; while in the Planirosti-a it is the 

 accessory gill which is wanting, the pseudobrancliia 

 being present. 



In the Sturgeons the spinal cartilaginous column is 

 prolonged into the long upper caudal lobe, and the skull 

 is one cartilaginous [liece, which varies in the length 

 and forms of its processes according to the species. 

 A number of sculptured bony shields encase the dorsal 

 and lateral aspects of the skull more or less completely. 

 These are generally considered to be parts of the 

 dermal skeleton, though they have a certain relation in 

 number and position with the cranial bones of an 

 osseous fish. Their texture is the same with that of 

 the shields that are imposed on the five angles of the 

 body. The floor of the cartilaginous skull is formed 

 of a dense thin bony plate, which from its position 

 has been named the occipito-sphenoid bone, and is 

 prolonged into the snout by a narrow continuation, 

 considered to represent the vomer, or as it is called by 

 some the ethmoid bone ; posteriorly the occipito-sphe- 

 noid forks, and extends backwards under the forepart 

 of the spinal column. The mastoid or paroccipital 

 cranial shield sends a bony plate of similar texture with 

 the occipito-S|)henoid one, downwards into the cephalic 

 cartilage. KiiUiker has examined the shields and bones 

 of Acipenser maccarii and of Scciphirhynchus, and 

 found them to contain bony corpuscles in accordance 

 with the general structure of ganoid bones. 



The fins, seven in number, are supported by crowded, 

 jointed, flexible rays, which are finely denticulated on 

 both sides ; the first ray only of the powerful pectorals 

 being stout, rigid, and bony. Near the vent are the 

 ventrals, which in this family are of small size. The 

 dorsal is situated far back above the anal. A large 

 swim-bladder sends a pneumatic tube to the bottom of 

 the stomach; and the ovisac opens freely into the cavily 

 of the belly by a funnel-shaped mouth. 



Order X.— SAUROIDS or LIZARD FISHES (Agassiz). 



This order is rather more comprehensive than the 

 Salamandroidei of Owen, as it includes some fossil 

 ganoid families ; but here we shall notice only its 

 existing members, the Lepidostids and Polypterids. 

 These two families differ from each other in their 

 skeletons, especially in the jaws, also in the nostrils, the 

 gills, in the stomach and cteca, in the first vertebral 

 joint, and in the caudal fins, as well as in other parts 

 of their structure. Their agreement is in their ganoid 

 scales, their valvular arterial stems, and in the cellular 



Vol. 



• Fleta I., c. 45, 46. 



or double air-bladder opening by a glottoid fissure into 

 the oesophagus. Both are said to have bony corpuscles 

 in their bones, as the Malacopteres have generally. 



Family I.— LEPIDOSTIDS (Lcpidosteidcc). 



These are elongated fishes, encased in strong ganoid 

 scales, mth sometimes a slender prolonged snout resem- 

 bling the bill of a gar-fish. In other species the snout 

 is shorter and broader ; it is constructed of the jaws, 

 palatines, nasal, and vomer. The Lepidostids are con- 

 fined to the waters of the United States and the adjoin- 



