FLATFISHES. NORMAN. 259 



trctis (Fig. 8 D, 8 E), Peltorhamplms (Fig. 8 G), 

 and Rhombosolea (Fig. 8 F), exhibit the typical 

 Pleuronectine arrangement, but in Psammodiscus, 

 Pclotrctis (Fig. 8 A), and Azygopus (Fig. 8 B), 

 the laminae are arranged in pinnate form, with an elon- 

 gate central rachis. In both the species of Colistium the 

 laminae are arranged in pinnate form, but radiate from 

 a very short rachis (Fig. 8 C) ; this condition appears 

 to be intermediate between the two types mentioned 

 above. 



The conclusion is that the median rachis has been 

 lost within the group Rhonibosoleinae, and that those 

 genera which exhibit the Pleuronectine arrangement are 

 not on that account to be regarded as related to the 

 Pleurouectinae. 



The family Paralichthodidse was erected by Regan 9 

 for ParaUchthodes algoensis from South Africa, which 

 differs from the Bothidae in having the eyes on the right 

 side, and from the PleurouectidaB in the arrangement 

 of the olfactory laminae, which radiate from a median 

 rachis. This character appears to be of less importance 

 than it was thought to be, and perhaps Paraliclithodes 

 should be included in the subfamily Pleurouectinae. 



The more specialised genera of the subfamily 

 Rhombosoleiuae, i.e. Ammotretis, Peltorhamphus and 

 Colistium, exhibit a certain general resemblance to the 

 members of the family Soleidae. This resemblance, which 

 is most marked in the last genus, is shown in the general 

 form of the body, the shape of the head, particularly its 

 praeorbital part, the small eyes, the symmetrical nasal 

 organs, the strongly curved jaws of the blind side, the 

 absence of teeth in those of the ocular side, and the 

 extension of the dorsal fin to the end of the snout. The 

 development of membraneous folds on the blind side of 

 the vertical fin-rays, the modification of many of the 

 scales on the blind side of the head to form filamentous 

 processes, and the fringed lower lip, are other Soleid 

 features. These Sole-like characters have evidently 

 evolved within the subfamily, and do not indicate 

 relationship to the Soleidae. The small eyes and barbel- 

 like processes on the head are probably related to 

 nocturnal habits; the shape of the anterior region of the 



"Ann. Durban Mus., II, 1920, p. 213. 



