1889.] NATURAL SCIENCES OF PHILADELPHIA. 245 



A REVIEW OF THE AMERICAN SPECIES OF STURGEONS 

 (ACIPENSERIDAE.) 



BY PHILIP H. KIRSCH AND MORTON W. FORDICE. 



In the following paper we have given the synonymy of the 

 Sturgeons or Aeipenseridae found in American waters, an analytic 

 key by which the species may be distinguished, and a list of nominal 

 species with identifications. All the species examined by us belong 

 to the Museum of the University of Indiana. Most of them were 

 collected by Dr. D. S. Jordan, to whom Ave are indebted for aid in 

 various ways. The variations due to age are extremely great in this 

 group, and some of the characters given here as distinctions may 

 prove to be of little value when a larger amount of material is 

 examined. There can, however, be little'doubt of the distinctions of 

 the six species here recognized. We feel also very certain that no 

 other species exist within our limits, and that all of the many nomi- 

 nal species should be referred to these six. This paper must be 

 regarded as provisional only, as helping to clear the way to a better 

 knowledge of the members of the group. 



Characters of the Aeipenseridae. 



The order of Glaniostomi contains among recent fishes but a 

 single family, Aeipenseridae which may be thus characterized: 



Body elongate, subcylindrical, with five rows of bony plates, a 

 median dorsal, and a lateral and ventral on each side. Each plate 

 has a median carina which terminates in a more or less developed 

 spine, which becomes blunt with age, while the ventral plates are 

 sometimes deciduous. The skin, between the bony plates is rough 

 with smaller, irregular plates and spicules of varying sizes. Head 

 covered with bony plates connected by sutures; snout produced, 

 depressed, subcylindrical, conical or subspatulate ; mouth small, 

 inferior, round or transverse, protractile, with thickened lips, and 

 toothless; nostrils large, double, in front of the eye, which is small, 

 lateral ; four barbels in a transverse series on the lower side of the 

 snout : maxillary distinct from premaxillary. Gills 4. An acces- 

 sory opercular gill. Pseudobranchire small or obsolete. No bran - 

 eheostegals. Gill-membranes united to the isthmus. Pectoral fins 

 placed low ; dorsal posteriorly ; anal somewhat behind it and 

 similar ; ventrals many rayed, behind the middle of body. Tail 



