1886.] NATURAL SCIENCES OF PHILADELPHIA. 233 



A REVIEW OF THE AMERICAN GASTER0STEID.5:. 

 BY CARL H. EIGENMANN. 



In this paper I have attempted to give the synonymy of the 

 American species of G aster osteidae with analytical keys for their 

 identification, and such notes as my studies of the group seem 

 to justify. The specimens examined all belong to the Museum 

 of the Indiana University. 



I am indebted to Dr. David S. Jordan for the use of his library 

 and for many suggestions. 



Analysis of Gene7-a of Gasterosteidse. 

 a. Snout not prolonged ; dorsal spines 3 to 11. 

 b. Innominate bones joined, forming a median plate on belly 

 behind ventral fins. 

 c. Gill membranes joined ; their posterior border free from the 

 isthmus ; spines small, mostly feeble. 

 d. Dorsal spines 7 to 11, weak, divergent ; innominate bones 

 with the outer edge stout and thick; the median part 

 scarcely ossified ; pubic bones long, weak, widely diver- 

 gent, leaving a <l-shaped naked area in front of ventral 

 spines ; body slender. Pygosteus. 1. 



dd. Dorsal spines 5, non-divergent, of moderate size; innomi- 

 nate bones united, forming a short, narrow but strong 

 ventral plate ; pubic bones weak, short, widely divergent, 

 leaving a subcircular space in front of ventral spines ; 

 body rather stout ; skin smooth. Eucalia. 2. 



cc. Gill membranes narrowly joined to the isthmus ; innomi- 

 nate bones large and strong ; spines of fins mostly 

 strong ; divergent ; dorsal spines 3 or 4 in number ; 

 pubic bones very broad, long and little divergent, 

 leaving a lanceolate-shaped, naked area in front of the 

 ventrals ; form robust ; skin mailed or naked. 



Gasterosteus. 3. 

 66. Innominate bones not joined, but each extending as a strong 

 process under the skin on outside of insertion of ventrals ; 

 the area between them flat and not ossified ; pubic bones 

 short and weak, not visible externally ; dorsal spines 

 strong, divergent, 4 in number ; gill membrane broadly 

 joined to the isthmus; body rather stout; the caudal 

 peduncle very slender ; skin smooth. Apeltes. 4. 



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