18 U.S. NATIONAL MUSEUM BULLETIN 282 



genera align them together and separate them from both the Ictalurus 

 and Pylodictis groups although they appear to occupy an intermediate 

 phylogenetic position (table 1). Among the many characters in 

 common are the reduced occipital process, the long adipose fin, the 

 general similarity in head and body shape, divergence from a normal 

 mode of 15 branched caudal rays, a shortened air bladder, an obsolete 

 post-temporal bone, a slightly reduced ectopterygoid, rather widely 

 separated anterior ends of the preoperculomandibular canals, similarly 

 shaped infraorbital canals, a short lateral line, and relatively few 

 vertebrae. Yet they seem to be distinct units. Prietella differs from 

 Noturus especially in the primitiveness or lack of ossification of the 

 first dorsal ray, the degeneration of ossified tissue at the anterior 

 base of the dorsal fin, especially the absence of the plate-like spine, 

 and in features resulting from subterranean life: depigmentation, 

 eyelessness, and interruption of the infraorbital and preoperculoman- 

 dibular canals. The anterior fontanelle is a small round opening in 

 contrast to the elongate slit or opening in all other ictalurids (see 

 Suttkus, 1961, fig. 5). 



The short, blunt, nonserrated, ungrooved condition of the pectoral 

 spine and eight pelvic rays are duplicated or approached in few kinds 

 of Noturus. iilthough Pylodictis and Ictalurus have a range that over- 

 laps their apparent underground relatives, which occur in central 

 Texas, Noturus and Prietella are geographically isolated; Prietella is 

 known only from one;.locality in the Rio Grande drainage of Mexico, 

 whereas Noturus ranges no farther southwestward than the Nueces 

 River, Texas. They are regarded as distinct genera, but are thought to 

 be related ; there is no suggestion that Prietella is related to any of the 

 other recognized groups of ictalurids. Indeed, the superficial similarity 

 of Prietella and certain forms in the subgenus Schilbeodes of Noturus 

 is striking. 



Due to the similarity of Noturus and Prietella, the following descrip- 

 tion of Prietella phreatophila Carranza (based on thirteen specimens of 

 which three were cleared and stained) is included (see also Carranza, 

 1954): standard length 34.0 to 52.8 mm.; anal rays 12 (in 1), 13 (1), 

 14 (6), and 15 (5) ; pelvic rays 8 (26 sides) ; soft pectoral rays 8 (7 sides) 

 or 9 (19); dorsal rays 6 (2) or 7 (11), see p. 19; internasal pores 2 (24 

 sides); preoperculomandibular pores 10 (1), 11.(21), and 12 (2); gill 

 rakers 10 (2 sides), 11 (4), 12 (7), 13 (10), and 14 (1) ; ribs 5 (5 sides) or 

 6 (1) ; precaudal vertebrae 7 (l),8(l),or9(l); caudal vertebrae 21 (1), 

 23 (1), or 24 (1); vertebrae anterior to anal fin origin 11 (1) or 12 (2); 

 total vertebrae 29 (1), 31 (1), or 32 (1) ; branchiostegal rays 8 (2 sides) 

 or 9(4). Caudal rays: upper simple rays 12 (1), 13 (3), or 14 (9); upper 

 lobe branched rays 6 (13); lower lobe branched rays 6 (1) or 7 (12); 

 lower sunple rays 12 (1), 13 (0), 14 (7), 15 (4), or 16 (1); lower-half 



