﻿308 AETHRODIRA. 



Genus HETEROSTEUS, Asmuss. 



[Das vollkommenste Hautskelet der bisher bekannten Thierreihe 

 (Inaug. Dissert. Dorpat, 1856), p. 7 {Heterostius).'] 



Syn. Ichthyosauroides, S. Kutorga, Zweiter Beitr. Geogn. u. Palaont. 



Dorpat's, 1837, p. 35 (inappropriate). 

 Chelonichthys, L. Agassiz, Poiss. Foss. vol. i. 1844, p. xxxiii. 



(name only, in part). 

 Asterolepis, L. Agassiz (non Eichwald), Poiss. Foss. V. G. R. 



1845, p. 89 (in part). 



A genus of enormous size, closely allied to Homosteus, but known 

 only from detacbed dermal bones. Head and trunk broad, the dorsal 

 aspect flattened ; scutes ornamented with large stellate tubercles, 

 and those of the upper surface of the head also marked with deep 

 sensory furrows. A single broad median dorsal shield upon the 

 trunk, with an inner longitudinal keel, and more or less acutely 

 pointed posteriorly ; the anterior dorso-lateral plate on each side 

 with a very large, forwardly-directed, antero-external process, and a 

 prominent condyle for articulation with the external occipital. 



Heterosteus asmussi (Agassiz). 



1837. Trionyx spinosus, S. Kutorga, Zweiter Beitr. Geogn. u. Palaont. 



Dorpat's, p. 9, pi. i. 

 1837. Humerus Trionychis, S. Kutorga, ibid. p. 17, pi. viii. fig. 1. 

 (?) 1837. Trionyx miliaris, S. Kutorga, ibid. p. 16, pi. vii. fig. 4. 



1844. Chelonichthys asmusii, L. Agassiz, Poiss. Foss. vol. i. p. xxxiii. 

 (name only). 



1845. Asterolepis asmusii, L. Agassiz, Poiss. Foss. V. G. R. pp. 92, 

 146, pi. xxx. fig. 1, pi. xxx. a. fig. 11. 



1845. Asterolepis, L. Agassiz (non Eichwald), ibid. p. 94, pi. xxxii. 



figs. 7, 11-13, 15-19. 

 1856. Heterostius hueckii, H. Asmuss, Das vollkommenste Hautskelet 



der bisher bekannten Thierreihe, p. 28. [Median dorsal plate ; 



University Museum, Dorpat.] 

 1856. Heterostius gracilior, H. Asmuss, ibid. p. 28. [Ditto.] 

 1856. Heterostius convexus, H. Asmuss, ibid. p. 28. [Ditto.] 

 1856. Heterostius eurynotus, H. Asmuss, ibid. p. 28. [Ditto.] 

 1856. Heterostius ingens, H. Asmuss, ibid. p. 29. [Median occipital ; 



University Museum, Dorpat.] 

 1856. Heterostius secundarius, H. Asmuss, ibid. p. 30. [Anterior 



dorso-lateral ; University Museum, Dorpat.] 



1856. Heterostius initialis, H. Asmuss, ibid. p. 31. [Ditto.] 



1857. Heterostius, C. H. Pander, Placoderm. devon. Syst. p. 82, pi. viii. 



