Order Isospondyli' 



COMPOSITE AUTHORSHIP 



Characters and Keys to Suborders 

 and Families 



HENRY B. BIGELOW 



Museum of Comparative Zoology 

 Harvard University 



Acknowledgments. Special thanks are due the following persons for their invaluable 

 help and cooperation in preparing the text and keys of this section : William W. 

 Anderson, James E. Bohlke, Daniel M. Cohen, J. R. Dymond, Robert H. Gibbs, 

 Jr., W. A. Gosline, Marion Gray, N. B. Marshall, Giles W. Mead, James E. 

 Morrow, Jr., George S. Myers, Albert E. Parr, and Robert R. Rofen. 



Characters of Living Isospondyli. Both premaxillary and maxillary bones are present 

 in most, but in a few these bones are greatly reduced or lacking (among Argentinoidea, 

 Part 4). In most the maxillaries form a part of the border of the mouth (see also 

 pp. II, 12, 17, 92, 95). The premaxillaries are only slightly protractile, if at all so, 

 except in the Phractolaemidae,^ some Alepocephalidae, and some Stomiatoidea (see 

 Bertin and Arambourg, 18: 2247), where they are protractile. The bone in the 

 ethmoid position above the vomer is unpaired in most but paired in a few (pp. 95, 96). 



There are four gill clefts, and in a few there is an open slit between the mandible 

 and the hyoid arch (Malacosteidae). 



1. With accounts of the included Suborders, Families, Genera, and Species by various authors as listed in the Table 

 of Contents. In this series of volumes, the Iniomi, treated as a Suborder of the Isospondyli by some authors, is 

 given the rank of Order and is dealt with in Memoir I, Part 5. 



2. A family of the Chanoidea, or so-called milkfishes, of the tropical Pacific. 



89 



