﻿310 ARTHRODIRA.. 



15142 S. Imperfect median occipital, shown from the inner aspect 

 and the posterior margin placed uppermost by Agassiz 

 (pi. xxxii. fig. 7), and figured 03- Pander {op. cit. pi. viii. 

 fig. I 10 ) ; the type specimen of H. ingens, Asmuss (p. 29, 

 no. 9), described as " scutum dorsale posterius." 



15142 t. Eight lateral occipital (" mastoid " or marginal, Pander, 

 pi. viii. fig. I 9 ), figured by Agassiz (pi. xxxii. figs. 15, 

 16), the glenoid extremity being placed uppermost ; 

 described by Asmuss (p. 32, no. 16) as " os multifixum " 

 of H. eurynotus. 



15142 U. Portion of similar bone; assigned by Asmuss (p. 32, 

 no. 15) to H. gracilior. 



15142 V. Bone figured by Agassiz (pi. xxxii. fig. 17) and identified 

 by Pander (pi. viii. fig. I 5 ) with the anterior extremity 

 of the postorbital; described by Asmuss (p. 32, no. 38) 

 as left " os incunneatum " of H. convexus. 



15142 W. Portion of bone identified by Pander (pi. viii. fig. I 3 ) 

 with the hinder half of the postorbital ; described by 

 Asmuss (p. 32, no. 17) as upper half of left " os inter- 

 jectum." 



The right half of a median dorsal plate of Heterosteus, from 

 Dorpat, is described by S. Kutorga 1 as the coracoid of a genus of 

 reptiles, Ichthyosauroides, allied to Ichthyosaurus. This is regarded 

 as the type of a distinct species of Heterosteus, H. kutorgce, by 

 Asmuss (op. dt. p. 29), and the original of the first of the under- 

 mentioned plaster casts is also assigned to it. 



15142 x. Hinder middle portion of small median occipital (" scutum 

 dorsale posterius," Asmuss, p. 29, no. 8), probably refer- 

 able to young individual of H. asmussi; original from 

 Dorpat. 

 Presented by Sir Roderick I. Murchison, K.C.B., about 1846. 



15142 y. Portion of left half of a similar bone, assigned to H. con- 

 vexus by Asmuss (p. 29, no. 10) ; original from Dorpat. 

 Presented by Sir Roderick I. Murchison, K.C.B., about 1846. 



Several bones found associated with those of Homosteus and He- 

 terosteus in the Lower Devonian of Livonia are also represented in 

 the Collection by plaster casts, presented by Sir Roderick I. 3Iur- 



1 Zweiter Beitr. Geogn. u. Palaont. Dorpat's, 1837, p. 35, pis. v., vi. 



