^%<- 



60 



intraspecific variation in the number and size of infraorbitals 2-4 in ageneiosids, 

 based on examination of a limited amount of material. 



Among the genera of auchenipterids, there is extreme variation in the 

 number, shape, and relative positioning of the infraorbital bones, which Ferraris ^ 

 (1988) used extensively in phylogenetic comparisons. While I agree that several of 

 his observations probably represent unique, derived characters, it appears that the 

 extreme degree of variation may in some cases be of limited value for determining 

 relationships; at least, this is the case among species of ageneiosids. Until more 

 data become available on variation, ontogeny of the ossification sequence, and 

 probable homologies of the various infraorbital elements, I defer using them in a 

 phylogenetic analysis of ageneiosid species. 



There is some variation among ageneiosids in the latero-sensory canals of the 

 head, but I have not made an extensive survey of this variability. In most species, 

 there appear to be relatively few pores passing to the surface, but the pores are 

 small and difficult to observe in whole, preserved specimens. Ageneiosus brevifilis 

 ondA. marmoratus have a number of star-like clusters of short canals on the dorsal 

 surface of the head, especially on the snout and near the eyes, and a row of similar 

 pores on the chin overlying the dentaries. Similar clusters were occasionally 

 observed in other species, but never appeared as prominent or numerous as in A. 

 brevifilis. 



The lateral-line canal exits from the upper half of the posterior margin of the 

 posttemporal bone and extends along the upper half of the trunk to the caudal fin. 

 The lateral hne is sinusoidal along its entire length, and gives off several short, 

 irregular rami that are directed posterodorsally and posteroventrally, passing to the 

 surface and ending in small pores. At the base of the caudal fin, the lateral line 

 bifurcates, and sends a branched ramus onto each lobe of the fin. The dendritic 

 structure of the lateral line is derived, and is apparently shared by all auchenipterids 



