264 
SIREN01DEI. _ - . - Jf 
Si/ /■/ 
Family LEPIDOSIRENIDiE. 
Cranial roof-bones few; no distinctly differentiated maxilla or 
premaxilla, and no marginal series of teeth above or below; jugular 
plates absent. Caudal fin diphycercal. Scales cycloid. 
f ^ oo /he/ /c•€*//■«?.££- 
— _ A' "/■ <N “4-. . • • 
?-7 S’-*'? ‘ Genus CERATODUS, Agassiz. 
Oft p 
f, /. 
/ 
, ■ ■■ 
[Poiss. Foss. vol. iii. 1838, p. 129.] 
Syn. Hemictenodus, 0. Jaekel, Sitzungsb. Ges. naturf. Freunde, 1890, 
p. 7 (in part). 
Body elongate, laterally compressed, covered with very large thin 
scales, superficially calcified ; head small and depressed, snout acute. 
Notochord persistent. Dental plates above and below triangular or 
irregularly ovoid in shape, with outwardly radiating, smooth ridges 
Fig. 40. 
Ceratodus forsteri, Krefft.—Open mouth, showing dentition : n, narial openings ; 
x, vomerine teeth xx, palatine dental plates; xxx, mandibular dental 
plates. 
forming a series of very large processes at the external margin, which 
are sometimes feebly denticulated. Paired fins acutely lobate ; dor¬ 
sal fin arising about the middle of the back, both this and the anal 
fin being continuous with the caudal. 
This definition is given on the assumption that the early Mesozoic 
teeth originally named by Agassiz pertain to a fish identical iu 
