Fishes of the Western North Atlantic 2 5 



desotoi; all of these occur in the western North Atlantic or Gulf of Mexico in fresh, 

 brackish, or salt water. Since A. sturio of the eastern Atlantic and Mediterranean has 

 sometimes been considered synonymous with A. oxyrhynchus, the relationship of these 

 two is discussed on p. 57. 



Most of the material for our study consisted of collections made in New York 

 {35'- 45-103) ^"d Quebec (83: 143-204; 84: 129-154). Supplementary data were 

 obtained by examination of the material at the Paris Museum National d'Histoire 

 Naturelle, the United States National Museum, and the Academy of Natural Sciences 

 of Philadelphia. 



The Descriptions are based on the Study Material listed for each species. An 

 explanation of terms, measurements, and counts is given on p. 'T,^,- The accounts of the 

 habits and geographical distributions are based upon published records and personal 

 observations. 



Many of the earlier authors who dealt with the taxonomy of Sturgeons based their 

 conclusions on differences associated with the age of the specimens, with the conse- 

 quences that they recognized several nonexistent species. Hence, among the refer- 

 ences, we use only those that we consider to be the most important from a taxonomic 

 point of view, and particularly those dealing with the life histories of the species. 



Characters. Body subcylindrical. Snout greatly extended, blade-like and flexible 

 in some, in others only slightly extended, if at all, and rigid. Mouth on lower sur- 

 face of head, protractile or not. Chin barbels prominent in some but lacking in others. 

 Dorsal fin situated far rearward; only one. Caudal fin more or less deeply forked, 

 with fleshy axis (enclosing notochord) extending rearward to tip of upper lobe, bending 

 upward beginning at base of fin ; heterocercal, wider below than above the fleshy axis. 

 Ventral fins well developed, abdominal in position. Fin rays much more numerous 

 than their basal skeletal supports. Pectorals with the first ray transformed in some 

 into an ossified ray, the fins otherwise without spines. Skin of trunk rearward from 

 eyes seemingly naked in some but actually with minute scattered Platelets; others 

 with five longitudinal rows of Scutes (large bony shields), the skin roughened else- 

 where with small scattered Dermal ossifications.* A continuous series of rhombic to 

 lanceolate Plates, closely set, on axis of caudal; the upper margin of caudal with a 

 dorsal fringe of large v-shaped Fulcra (spine-like scales), each representing the fusion 

 of a pair of opposing plates. Teeth minute, if present. Branchiostegal rays absent. 



Skeleton cartilaginous for the most part, the primitive cartilaginous cranium 

 (chondrocranium) persisting and growing throughout life; ossification chiefly repre- 

 senting development of membrane bones (p. 4) in regions of skull, jaws, and pectoral 

 girdle. Upper jaw not articulating with skull either in the ethmoid region or in the 

 sphenoid. Premaxillary bone fused with maxillary. Pectoral girdle fused with clavicle. 



4. There is no definite terminology for the plates or granules found in the skin between the regular rows of bony 

 shields; they have been variously called: stellate plates, stellate roughnesses, stellate ossifications, minute rough 

 spinules, small prickle-like plates {43: 104-106), dermal plates, and small spinous asperities (Ryder, The Sturgeons, 

 with an account of experiments bearing upon Sturgeon culture, 65: 231-328). In the present manuscript they are 

 called "dermal ossifications." 



