Devonian Fish-Fauna of SpitzhGrrjen. 11 



have been either a, long spine or a problematical elongated 

 element sueh as has been described bj Davis "^ in Oracanthus. 

 There is thus no justification for specifically distinguishing 

 the fossil from the typical })lates of P. arenatiis^ with which 

 it is associated. 



Form, and Loc. Ironstone, Miniers Valley. 



Subclass DIPNOI. 

 Order AimiRODIRA. 



Family (uncertain). 

 Genus AsTEROPLAX, nov. 



Dermal armour robust, superficially ornamented with coarse 

 rounded tubercles, more or less fused into radiating and partly 

 reticulated ridges. Head longer than broad ; bones of cranial 

 roof few and large, comprising a median occipital, bounded iu 

 front by a pair of trapezoidal plates, which meet in the middle 

 line and occupy the entire width of the shield, these immedi- 

 ately succeeded forwards again by a large diamond-shaped 

 median element and a pair of antero- posteriorly elongated 

 lateral plates; [rostral region unknown]. 



Though known only by the imperfect fossil described 

 below, the reference of this genus to the Arthrodira seems to 

 be justified by the arrangement of the richly ornamented 

 cranial roof-bones. According to existing definitions, how- 

 ever, it cannot be placed in any known family. 



Asteroplax scabra, sp. n. (PI. III.) 



Cranial shield nearly flat posteriorly and the tubercular 

 ornament especially coarse. Breadth of median occipital 

 plate about equal to that of one of the posterior paired plates, 

 and the latter much longer than broad ; second median plate 

 nearly as broad as the median occipital. 



Notwithstanding the difficulties presented by the interpre- 

 tation of the type and only known specimen of A. scabra, it 

 will probably be admitted without hesitation that the aspect 

 of the fossil shown in PL III. fig. 1 exhibits part of a cranial 

 shield with remains of an adjoining cheek-plate (a;). It also 

 seems reasonable to assume that the narrower and more finely 

 ornamented portion of the fossil is the base of the rostral 

 region, the broader end the occipital ; and the fortunately 



* J. W. Davis, Ti'ans. Roy. Dublin Soc. [2] vol. i. p. 529, pi. Ixii. 

 fig. 13, 1)1. ixv. figs. 3, 4. 



