PLATE 1 



Sensory canal system of two species of Ictaluridae (slightly diagrammatic). 



Figure 1. Dorsal view of Noturus exilis Nelson. 



Figure 2. Dorsal view of PylodicUs olivaris (Rafinesque). 



(IO=Infraorbital canal; LAT=Lateral canal; LI and L2=First and second infraorbital 

 canal pores; Nl, N2, and N3=First, second, and third supraorbital canal pores; 0M9, 

 OMIO, OMll, 0M12=Ninth through twelfth preoperculomandibular canal pores; POM= 

 Preoperculomandibular canal; SO^Supraorbital canal.) 



LI and N2 are fused and there are ten preoperculomandibular pores in Noturus exilis. 

 In Pylodidis, these pores are unfused, Nl and N2 are located more anteriorly, the infra- 

 orbital canal extends diagonally backward, and there are twelve preoperculomandibular 

 pores. The canal arrangements in the species of Noturus, Prietella, Trogloglanis, and Idalurus 

 are essentially as in Noturus exilis, but the number of preoperculomandibular pores and the 

 fusion of LI and N2 varies (see p. 11). Satan eurystomus Hubbs and Bailey is much like 

 Pylodidis, but Nl is more posterior in position and LI and N2 are fused. 



