adipose deposits in the fin did not preclude an accurate count of anterior and 

 posterior principal rays. The posterior anal pterygiophore typically included two (or 

 rarely three) lepidotrichia, counted separately, which often appeared superficially 

 joined at their base, but are distinct elements as revealed by radiography or 

 counterstaining. Vertebral counts were made from radiographs and counterstained 

 specimens, and included one for the fused PUl + Ul centra and six for the Weberian 

 complex. Preanal vertebrae are those with hemal spines anterior to the first 

 proximal anal pterygiophore. Counts of pleural ribs are of pairs as determined from 

 radiographs taken of specimens from the dorsal profile or from alizarin 

 preparations. Counts of branchiostegal rays are very difficult in ageneiosids because 

 the gill membranes are broadly fused to the isthmus and the head is greatly 

 flattened; in this study, determination of branchiostegals, as well as gill raker 

 number, was facilitated by making an acentric incision anteriad from the ventral 

 point of the opercular opening and carefully bending the branchiostegals outward. 

 Visibility of the branchiostegals was often enhanced by directing a narrow fiberoptic 

 beam through the flesh. In some cases, questionable counts of branchiostegals were 

 verified by examination of dorsoventral radiographs. Gill raker counts are those of 

 the outer row on the first arch. " '■ . . • ' ' ; \ " C^/ 



Tissues selected for study with a scanning electron microscope (SEM) were 

 prepared by dehydration through a graded ethanol series, dried in a critical point 

 dryer using liquid carbon dioxide as the transition medium, then mounted on 

 observation stubs and sputter coated with palladium-silver prior to examination on a 

 Hitachi S-570 SEM using an accelerating voltage of approximately 65 Kv. Tissues 

 used for light microscopy were dehydrated and cleared through an ethanol-xylene 

 series, infiltrated and embedded in paraffin, then sectioned on a rotary microtome 

 and mounted on slides using conventional histological techniques (Humasson 1979). 

 Sectioned tissues were stained with Harris hematoxylin/eosin Y or a modified 



