Classi^c<itiOfi of the Order Iniomi, 129 



mesetlimoid, so that the lateral etlniioids are separated and 

 are almost entirely below the level of tiie parasphenoid ; the 

 mesetlimoid bears a prominent median ridge. The jaws, tlie 

 palatine attachment, and the post-temporals are as in Chloro- 

 phthalmus ; the mesopterygoid is well-developed, but does 

 not overlap the parasphenoid ; the suboperculum and branchio- 

 steofals are not curved upwards behind the operculum ; except 

 for the post-temporal attacliment the pectoral arch is very 

 niuch as in Aulopus; the pelvic bones are small triangular 

 plates. 



There are 32 vertebrae ; there are 12 pairs of ribs, the last 

 7 inserted on parapopliyses which increase in length back- 

 wards ; series of epineurals and epipleurals are present; there 

 are 3 epurals and 2 uroneurals and the last centrum is up- 

 turned. 



Lampanyctus is a much more specialized form, with slender 

 adherent maxillary and oblique suspensorium ; tiie skull is 

 as broad as long, but agrees with that of JSeoscopelua in 

 essentials. The vertebral column has 35 vertebrte ; all the 

 ribs are inserted on parapophyses. 



Suborder 2, Alepidosauroidea. 



Head and body compressed ; caudal well developed, free 

 from the anal ; pectorals low ; pelvics 6-13 rayed, close 

 together, far behind the pectorals. Mouth large, not pro- 

 tractile; strong pointed canines in the lower jaw and on the 

 palatines ; prajmaxillary and maxillary long and slender, 

 firmly united distally. Palatine large, vertically expanded 

 anteriorly, where it is firmly attached by its upper edge to 

 the frontal and by its inner face to the side of the ethmoidal 

 region ; mesopterygoid rather small. Prjeoperculum narrow, 

 nearly vertical ; suboperculum entirely below operculum ; 

 interoperculuni reduced ; 6 to 8 branchiostegals. Ethmoid 

 without median keel or lateral processes ; parasphenoid 

 sl(^nder ; a basisphenoid ; no orbitosphenoid. Upper fork of 

 post-temporal cotniecttd by ligament with epiotic, but nearly 

 meeting its fellow above the supraoccipital ; cleithrum at- 

 tached to supracleithrum near upper end of the latter, which 

 runs obliquely downwards and backwards and has the upper 

 postcleithrum attached to its distal end. Pelvic bones 

 simple rods or triangular plates. No upturned centra at the 

 base of the caudal fin. No air-bladder. 



This suborder contains a few deep-sea fishes with the 

 skeleton rather weakly ossified. 



Ann. & M(uj. N. Hist. Ser. 8. Vol. vii. 9 



