7 o Memoir Sears Foundation for Marine Research 



orbital (maxillary auctorum). A peculiar wedge-shaped Blind pocket in skin of gular 

 region. Tongue bifurcate-spatulate. Three Modified scales bordering anus; median 

 scale, anterior to anus, a large shield-shaped plate; lateral plates elongate and slightly 

 curved. Other characters those of the Order. 



Species. Currently seven species are recognized in North American waters, but 

 detailed studies that are in progress may show that two of these forms are only 

 subspecifically distinct. There is some indication of hybridization, but verification of 

 this must await further study. L. oculatus, osseus, platyrhincus, and spatula are treated 

 in the following account. 



Key to Species of the Western North Atlantic 



I a. Total gill raker count on left outside arch, 59—81 (70 specimens); palatines of 



adult with a series of enlarged teeth. Subgenus Atractosteus Rafinesque 1820. 



2a. Lateral-line scales, 58—62 (25 specimens); diagonal rows between insertion 



of pelvic and origin of dorsal fin, 34—38; predorsal scales, 48—54. 



3a. Total gill rakers on left outside arch, 59-66 (20 specimens); females 



maturing at a larger size, probably not less than 600 mm; anterior body 



scales of 400-mm specimens finely serrated on posterior border. 



spatula Lacepede 1803, p. 83. 

 3b. Total gill rakers, 67—81 (5 specimens); females maturing at a smaller 

 size, 470 mm; anterior body scales of 400-mm specimens strongly ser- 

 rated on posterior border, tristoechus (Bloch and Schneider) 1801. 



Fresh waters of southwestern Cuba and Isle of Pines; not 



yet recorded for salt water but likely to be found there. 



2b. Lateral-line scales, 51—56 (60 specimens); diagonal rows between insertion 



of pelvic and origin of dorsal fin, 28—32; predorsal scales, 43—48 (usually 



44—47). tropicus (Gill) 1863. 



Rio Usumacinta of Guatemala and 



Mexico and tributaries of Lake 



Nicaragua and Rio San Juan in 



Costa Rica on the Atlantic slope, and 



from Pacific drainage of Chiapas, 



Mexico (Miller, 48: 230, 23 1).* 



Atractosteus bocourti Dumeril 1870; 



mouth of (Rio) Nagualate, I4°N. 



lb. Total gill rakers, 14-33 (148 specimens); palatines of adult without enlarged 



teeth. Subgenus Lepisosteus Lacepede 1803. 



4a. Snout's least width 13—25.5 times in its length (specimens more than 50mm 



long). osseus (Linnaeus) 1758, p. 75. 



4b. Snout's least width 4.5— 11 times in its length (specimens more than 50mm 



long). 



8. There are no records from salt water on the Atlantic side but L. tropicus is common in the tidal zones of the 

 Pacific drainages. 



