Evolution of (he Order Ilderosomatn. 403 



Subfamily 2. Platopiirtxm. 



Pelvic fill of blind side short-based ; pelvic fiii of oculur 

 side cloiip;ate, extending forward to theurohyal, supported by 

 a cartilaginous plat.o placed in advance of the cleithra. Vcrtc- 

 braj 37-4.'J (*J-10 + 27-3o) ; parapopliyses in pr^ecaudal 

 rej^ion connected or united as in the Paraliolitliin.c ; caulal 

 vertebriR wilh well-developed transverse ai)i)|)hyses. 



Principal <^enera : — Arnoqlossus, Anlicitharus, Cliaacano- 

 psetta, Pelecanic/ithf/.t, iSc(Cu/)Sy Engi/prosopon, Lctiopa^ Mono- 

 lene, Trichopsctta, Platophrya^ J^epidopsetta, Lophonectes, 

 from tropical and temperate seas. 



Jn the small-mouthed L<rops the jaws and dentition are un- 

 equally diiveloped on the two sides, just as in Elro/ms. 



I have examined skeletons of Arno(/lotisHs (vertebriu 10 + 33), 

 Flatophrys (10 + 29), and Lophonectes (10 + 31). 



Subfamily 3. Botuixje. 



P>oth pi Ivic tins elongate, extending forward to the urohyal, 

 su])ported by cartilaginous plates placed in advance of the 

 cleithra. Vertebrai 3-3-41 (9-12 + 25-31); parapopliyses in 

 precaudal region separate ; caudal vertebrae with well- 

 developed transverse apophyses. Jaws and dentition equally 

 developed on both sides. 



Genera : — Bvthus, Lepidurlionihus, Zeugopterus, and Phnjno- 

 rJionibiis, from the North Atlantic and Mediterranean. 



1 have examined skeletons of Bothus (vertebras 11 + 25), 

 Lepidur/iomhus {9 + Sl), Zeugopterus {'d -{-iC), and PUrif no- 

 rhombus (10 + 2G). 



Family 2. Pleuronectidae. 



Dextral, except for reversed examples in certain species. 



Nerve of the left eye always dorsal. Olfactory laminie 



slightly raised, jjarallel, without rachis. Egg without oil- 

 globules. 



Subfamil}' 1. Pleuronectinje. 



Anterior part of dorsal fin posterior to nasal organ of blind 

 siile ; pelvic fins short-based, supported by the pelvic bones 

 posterior to the cleithra, similar in form and symmetrical, or 

 the fin of the eyed side median. Pectoral radials present ; 

 hvpocoracoids nai rowed forward below. Vertcbrje 35-65 

 ( lo-lt'i + 23-52;; pra^caudal parapopliyses separate, divergent. 



