1894.J SALMONOTD FISHES OF THE ENGLISH CHALK. 663 



length. Further, it is known that the double suprainaxilla is not 

 quite constant in the Clupeoids, Elopines, and their allies. It 

 may also be argued that, as Dr. G-unther admits to the Clupeidee 

 Hying fishes with a gular plate (Elops, Megalops), there is no 

 reason for excluding from the Salmonidse any primitive fishes 

 which differ only from the living members of this family in the 

 possession of such a plate. Nevertheless, so far as the present 

 writer is aware, supramaxillaries of the form described above in 

 Osmeroides and Aulolepis have not hitherto been observed in any 

 Salmonoid, while they are a very common feature among 

 Clupeoids and Elopines. The two Cretaceous genera under dis- 

 cussion may therefore be provisionally associated with the latter. 

 The fishes named Osmeroides from the Chalk of Mount Lebanon 

 may also be placed here, for they likewise exhibit a large gular 

 plate ; and Elopopsis is already assigned to the same systematic 

 position by common consent. Elops and Megcdops, indeed, have 

 many more close allies in Cretaceous and early Tertiary strata 

 than has hitherto been suspected, and the type they represent 

 seems to have been dominant among the earliest Physostomi. 



EXPLANATION OF THE PLATES. 



Plate XLII. 



Fig. 1. Osmeroides lewesiensis ; fish from ventral aspect, two-thirds nat. size. 

 a., base of anal fin ; d., dentary ; git., gular plate ; mx., maxilla ; 

 op., operculum ; pet., pectoral fins ; plv., pelvic fins ; s.mx.z, posterior 

 supramaxillary ; s.op., suboperculum. [P. 7188.] 



2. Ditto ; hinder portion of cranial roof, upper aspect, fr., frontal ; 



pa., parietal ; s.t., supratemporal ; sp.o., supraorbital ; sq., squamosal. 

 [4295.] 



3. Ditto ; side view of head. 3 a. Eostral region of same specimen, upper 



aspect, br., branchiostegal rays ; m.pt., metapterygoid ; d., dentary; 

 ectp., ectopterygoid ; eth., ethmoid; fr., frontal; mx., maxilla; op., 

 operculum ; orb., orbit ; p.op., preoperculum ; pt.o., postorbital ; 

 qu., quadrate; s.mx. i, i, supramaxillaries: s.op. suboperculum. 

 [4296.] 



4. Ditto ; right quadrate (qu.), metapterygoid (m.pt.), and symplectic 



(sym.), outer aspect. [P. 5680.] 



5. Ditto ; left maxilla (mx.) and supramaxillaries (s.mx. x, 2), outer aspect. 



5 a. Symphysis of mandible, oral aspect, showing attachment of 

 teeth. [49891.] 



6. Ditto ; right mandibular ramus, outer aspect. ag., angular ; d., 



dentary. [4296.] 



Plate XLIII. 



Fig. 1. Elopopsis crassus ; lateral view of head, two-thirds nat. size. 1 a. Upper 

 view of ethmoidal region. 1 b. Left premaxilla, outer aspect, 1 e. 

 Left dentary, outer aspect, eth., ethmoid ; fr., frontal ; md., man- 

 dible ; mx., maxilla ; orb., orbit ; p.op., preoperculum ; pmx., pre- 

 maxilla ; pt.o., postorbital; s.mx., supramaxillary; s.o., suborbital. 

 [Willett Collection, Brighton Museum, no. 61.] 



2. Aidolepis typus ; imperfect fish, dorsal aspect. 2 a. Eight mandibular 



ramus, ag., angular; ar., articular; d., dentary; d.f, dorsal fin; 

 fr., frontal ; pa., parietal ; sq., squamosal. [P. 5681.] 



3. Ditto; right frontal, upper aspect. [P. 1854.] 



