1904.] OSTEOLOGY OF THE ELOPID^ AND ALBULIDjE. 71 



prehension at all. A. similarly constituted mouth occurs in the 

 MormyridfB. The right and left premaxillse of Mormyroid fishes 

 are fused, and the suture obliterated (except in Gymnarchus). 

 A similar condition is said to exist in Pantodon. In Chanos, 

 Chatoessus, and Gonorhynchus the premaxilla alone bounds the 

 gape above, and is devoid of teeth. 



The exceptional, and apparently useless, backward prolongation 

 of the maxilla of Coilia is a well-known feature of that genus, and 

 claims but a passing mention. 



There are two surmaxilla3 above each maxilla in Coilia, En- 

 graulis, Clupea, Dussumieria, Chirocentms, Slops, Megalojjs, and 

 Alepocephalus, one in Chatoessus and Albula, and none in Ghanos, 

 Arapaima, Heterotis, Osteoglossum, the Mormyiidee, Rijodmi, 

 Kotoptei-us, and Gonorhynchus. Two surmaxilla? are present in 

 the Mesozoic families Pholidophoridee, Leptolepidse, and Oligo- 

 pleuridse. 



Mandibular Series. — The angular bone is distinct in Arapaima, 

 Heterotis, Osteoglossum, Notojjteriis, and most Clupeoids, but not 

 in Coilia and Engraidis, nor in the Mormyridse, Hyodon, Albula, 

 Elops, and Megalops. In Notopterus the angular is a much larger 

 bone than usual. The endosteal and ectosteal parts of the articular 

 bone are distinct and separable in Arapaima ; and, according to 

 Hay (Zool. Bull. ii. 1, 1898, p. 37), they are also distinct in the 

 Cretaceous genus Xiphactinus. He shows that Cope's interpre- 

 tation of the mandibular bones of this form was entirely erroneous. 

 Since the remark of Owen's (Anat. of Yert. i. 1866, p. 123), that 

 in Arapaima there is a superadded bony piece answering to the 

 surangular of Reptiles, is credited by so recent a writer as Smith 

 "Woodward (Brit. Mus. Cat. Foss. Fish. iii. 1895, p. xix), it may 

 be well to point out that this superadded bone, marked 29 a in 

 Owen's fig. 88, is but the endosteal ai-ticular displaced. In 

 Gymnarchus, Hyodon, Albida, Elops, and Megalops the endosteal 

 and ectosteal components of the articular would probably separate 

 with prolonged maceration, for the suture between them is clearly 

 visible, but I was unable to submit the material in hand to such 

 treatment. As a rule the suture is not visible in Teleostean 

 fishes. 



In some forms the posterior part of the surface for the articu- 

 lation with the condyle of the quadrate is formed by the angular, 

 the part of the angular bone concei'ned having a distinctly end- 

 osteal appearance. Such is the case in Gonorhynchus, Arapaima, 

 Albida, Megalops, Elops, Gymnarchits, Hyodon, and Heterotis, but 

 in Osteoglossum, Notopterus, and the Olupeid^e the articular facet 

 is formed by the endosteal articular alone. In JSfotoptertis and 

 the Clupeida3 the angular bone has the appearance of an ectosteal 

 bone. 



Except in a few forms {e.g., Arapaima, Petrocephalus, Engraidis, 

 Chatoessus, Bussumieria) there is a distinct bone lying usually in 

 front of the endosteal articular and on the inner (lingual) surface 



