Evolution of the Order Ileterosotnata. 495 



Subfamily 3. Rhombosolein&. 



Dorsal fin extending forward on snout above nasal organ of 

 blind side ; pelvic fins formed as in the Platophrinas, that of 

 the eyed side median, extending forward to the urohyal, 

 supported by a cartilaginous plate in advance of the cleithra; 

 that of the blind side small or sometimes absent. No pectoral 

 radials, the rays inserted on the hypercoracoid ; hypocoracoids 

 narrowed forward below. Vertebral column formed as in the 

 Pleuronectinas, the proecaudal parapophyses not united. 

 Mouth asymmetrical ; jaws of the blind side strongly curved, 

 those of the eyed side toothless. 



Qenersn—Rhombosolea, Ammotretts, and Peltorhamphus 

 from Southern Australia and New Zealand, with Oncopterus 

 from Patagonia. 



I have examined the skeleton in Rhombosolea (vertebras 

 10-1-21) and Peltorhamphus (9 + 27). 



Division 2. 8oljeifo rmes. 



Mouth small, terminal, subterminal, or inferior, the lower 

 jaw never prominent ; j:iws of the blind side toothed, strongly 

 curved, the convexity of the lower fitting the concavity of the 

 upper ; jaws of the eyed side not or but feebly toothed; prse- 

 opercular margin not free. Nasal organs symmetrical in 

 position ; olfactory laminse arranged transversely to or 

 radiating from a central rachis. Optic chiasma dimorphic, 

 the right or the left nerve dorsal without reference to dex- 

 trality or sinistrality. No post-cleithrum ; no pectoral 

 radials, the rays inserted on the hypercoracoid ; hypocoracoid 

 reduced ; pelvic fins supported by the pelvic bones, which 

 are dependent from the lower extremities of the cleithra, 

 which do not reach the ventral profile ; praecaudal para- 

 pophyses united or connected by a bridge to form closed 

 haemal arches ; no ribs. 



Family 1. Soleidae. 



Dextral. Caudal fin separate or not ; pectorals often 

 present ; both pelvic fins usually developed, but that of the 

 blind side sometimes vestigial or absent, that of the eyed side 

 sometimes median, with extended base. Vertebras 28-57 

 (9-10+19-48). 



Principal genera : — Solea, Synaptura, 2Esopia, Achirus, 

 Pardachirus, Liachirus, Gymnachirus } Apionichthys, mostly 



