GAR-PIKES. 77 



The Shovel-nosed Sturgeon, Scaphirhynchus platyrhynchus, 210, shovel- 

 of the Mississippi and other rivers of the Southern States of North nose. 

 America is confined to fresh water. It differs from the true 

 Sturgeons of the genus Acipenser in the rostrum being long and 

 flattened, in the absence of open spiracles, and in the union of the 

 longitudinal rows of scutes beneath the dorsal fin to form a scaly- 

 armour investing the tail, whereas in the Sturgeons proper the 

 rows of scutes remain distinct as far as the tail. 



Lepidosteiformes (Gar-pikes). 



The Lepidosteiformes or iEtheospondyli are a small suborder 

 including two families, the Aspidorhynchidse and theLepidosteidae, 

 the former with extinct fishes only. The body is covered with 

 thick, rhombic scales, with a hard superficial layer of ganoin ; 

 they are arranged in oblique rows and are covered by a thin skin. 

 All the fins have fulcra; the fin-rays are branched and jointed at 

 their ends. The dorsal and anal fins are single and short-based, 

 and their endoskeletal elements are as numerous as the dermal 

 fin-rays. The pectoral fin has one row of basal bones (pterygia) 

 carrying the dermal fin-rays * ; the pelvic fins have not a series 

 of basal cartilages. There is no infraclavicle in the pectoral girdle, 

 and there is no pelvic girdle. The spiracle is wanting ; the snout 

 is elongated ; in the mandible are splenial and coronoid bones ; 

 the vomerine bone is paired; there are no jugular plates; the 

 opercular apparatus is complete ; between the preopercular bone 

 and the orbit are one or more rows of postorbital bones. 



The Aspidorhynchidse (213, and fig. 44, p. 78), are long-bodied 

 fishes with a pointed preoral rostrum, and deep, rhomboidal, un- 

 equal scales. The fins are small, the fulcra weak ; the caudal fin 

 is homocercal, i. e. with symmetrical outline and without obvious 

 uptilting of the vertebral axis. The vertebral centra are either 



* The preparation marked 217 shows not merely the characters of the 

 pectoral fin-skeleton of Lepidosteus, but may be taken to illustrate the 

 distinctive features of the astylopterygian fin generally. The dermal fin- 

 rays are strongly developed and form the most important part of the fin, 

 while the basal parts of the skeleton, the pterygia, are reduced as compared 

 with those of the stylopterygian fin, and are contained in a small muscular 

 mound which projects but little from the side of the body. 



