G36 On the Anatomy tCr. of the Order Discocepliali. 



only at the anterior end of the latter^ capable of a certain 

 amount of independent movement. Palatine elongate, 

 attached by its upper edge to the lateral ethmoid ; pterygoid 

 and mesopteiTgoid ankylosed; suspensoriura, branchial, and 

 opercular bones otherwise typically Percoid. Skull broad, 

 very strongly depressed, with flat or concave upper surface; 

 basisphenoid and alisphenoids absent; exoccipital condyles 

 transversely expanded, wide apart ; nasal and prseorbital 

 firmly united to each other and to the lateral ethmoid ; 

 number and arrangement of other bones of skull as in the 



Fiff. 2. 



eoc epo 



opo eoc J, 'Ooc pro 



Remora dypeata. Skiill from above (A) and below (B). 



V, vomer ; eth, mesethmoid ; leth, lateral ethmoid ; pror, prseorbital ; 

 M, nasal ; /, frontal ; p, parietal; soc, supraoccipital ; ex, exocci- 

 pital ; boc, basioccipital ; epo, epiotic ; opo, opistbotic ; pto, pterotic ; 

 spo, spbenotic ; pro, prootic ; psp, paraspbeuoid ; ;?<^, post-temporal. 



Perciformes. Vertebrae 23 to 30 ; ribs and epipleurals 

 inserted together on strong transverse processes. Pectoral 

 arch of the Perciforra type, except that the supracleithriim 

 is reduced and 3 radials are in contact with the hypocora- 

 coid ; pelvic bones directly attached to the cleithra. 

 Two families may be recognized : — 



Family 1. Opisthomyzonidae. 



Disc of about 6 segments, small, narrow, not extending 

 forward to the interorbital region, its width about ^ the 

 width of head. Vertebrae 23 or 24. Dorsal fin longer than 

 anal ; caudal widely forked. 



Opisthomyzon glaronensis from the Upper Eocene of 

 Switzerland (Wettstein, Mem. schweiz. Palaeont. Ges. xiii. 

 3886, p. 82, pi. vii. fig. 10 ; Storms, Ann. & Mag. N. H. (6) 

 ii. 1888, p. 73 : Cope, Amer. Nat. xxiii. 1889, p. 355). 



fj 



