﻿304 ARTMRODIRA. 



1889), p. 44: MacropetalichtJiys rapheidolabis, Norwood 

 and Owen, Amer. Journ. Sci. [2] vol. i. (1846), p. 871 : 

 Agassichthys sullivanti and A. manni, J. S. Newberry, Bull. 

 National Institute, 1857, p. 3 : MacropetalichtJiys manni % 

 J. S. Newberry, Amer. Journ. Sci. [2] vol. xxiv. (1862), 

 p. 75. — Corniferous Limestone (Lower Devonian) ; Ohio, 

 [The type species ; E. D. Cope Collection, Philadelphia.] 



Genus HOMOSTEUS, Asmuss. 



[Das vollkommenste Hautskelet der bisher bekannten Thierreihe 

 (Inaug. Dissert. Dorpat, 1856), p. 8 (Homostius).] 



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

 1845, p. 89 (in part) ; H. Miller (non Eichwald), footprints of 

 the Creator, 1849, p. 70 (in part). 



Head and trunk broad, the dorsal aspect flattened ; scutes orna- 

 mented with stellate tubercles ; caudal region destitute of armour. 

 Occipital elements of cranial shield constituting more than half of 

 its length ; orbits completely surrounded, the preorbital and post- 

 orbital plates forming the narrow outer bar ; a distinct small median 

 bone over the pineal region, not perforated ; mandibular rami sutur- 

 allv united at the symphysis, apparently toothless. A single broad 

 median dorsal shield upon the trunk, with an inner longitudinal 

 keel, and obtuse posteriorly ; two dorso-lateral plates on each side, 

 the anterior relatively large, with a well-developed, forwardiy- 

 directed, antero-external process, but no prominent condyle for arti- 

 culation with the external occipitals. [Ventral armour unknown.] 



The known species of this genus attain a large size, the width of 

 the body-shield in H. milleri being not less than 028. 



Homosteus formosissimus, Asmuss. 



1844. Asterolepis, L. Agassiz (non Eichwald), Poiss. Foss. V. G. R. 

 p. 96, pi. xxxii. tigs. 2, 9, 10. 



1856. Homostius formosissimus, H. Asmuss, Das vollkommenste Haut- 

 skelet der bisher bekannten Thierreihe, p. 35. 



1856. Homostius cataphr actus, H. Asmuss, ibid. p. 36. [Median occi- 

 pital ; University Museum, Dorpat.] 



1856. Homostius lotus, H. Asmuss, ibid. p. 36. [Ditto.] 



1856. Homostius ponderosus, H. Asmuss, ibid. p. 37. [Lateral occipital ; 

 University Museum, Dorpat.] 



1856. Homostius anceps, H. Asmuss, ibid. p. 39. [Bones ; University 

 Museum, Dorpat.] 



1857. Homostius, C. H. Pander, Placoderm. devon. Svst. p. 74. pi. viii. 

 figs. 2, 6, 7. 



