212 Frederick Chapman : 



arrangement of the elements of the cranidial shield necessitates the 

 removal of this interesting Australian Devonian type of fish to tho 

 latter family. 



Generic and Specific Relationships. — The Australian specimens 

 agree with Phlyctaenaspis (Traquair, 1890) rather than with Cocco- 

 steus, in the more ovate form of the cranial shield, and in the fusion 

 of the separate elements with the exception of the ethmoidal. Traquair 

 has shown 1 that the notch in the external angle of the cranial shield 

 in Phlyctaenaspis was occupied by a small plate, which he terms 

 the angular, and which is absent in Coccosteu* ; the remains of this 

 plate are seen on the left side of the Buchan specimen of the 

 variety confertituberculata, here described. 



The Victorian specimens agree more closely with the Canadian 

 species Phlyctaenaspis acadica, Whiteaves sp., than with the- 

 English, P. anglica, Traquair, in having the tuberculatum somewhat 

 regularly arranged in concentric lines parallel to the margin of the 

 plates. 



Additional Description of Phlyctaenaspis australis, McCoy sp. 



The figured specimen (loc. cit., pi. XXXV., fig. 7) of McCoy shows 

 definite sensory canals, and under a lens the sutures can be partly 

 deciphered. The latter present some difficulty as they are closely 

 fused. The disposition of these lines shows that the specimen con- 

 sists of nearly two-thirds of the cranial shield in the anterior 

 portion, the fracture of the .posterior margin representing the 

 anterior border of the left external occipital, the posterior of the 

 central plates, and a part of the anterior of the median occipital; 

 the fractured margin then cuts longitudinally through the right 

 marginal, along the sensory canal, emerging about the middle of 

 the plate (see pi. XX., fig. 3). The sutures and sensory canals ara 

 disposed, so far as they are visible, exactly as in Phlyctaenaspis. 



Measurements. — The actual width of the holotype of Phlyctae- 

 naspis australis is 55 mm., and the greatest length, .'55.5 mm. The 

 cranial shield, when complete, would approximately measure 55.25 

 nun. in length. 



Description of Phlyctaenaspis australis, var. confertituhercxdata, 



nor . 

 In this variety the tuberculate ornament is very dense, and the 

 tubercles smaller and more prominent. They are, moreover, 



1 Ann. Mag. Nut. Hist., ser. vi., vol. \h., 1894, i<. 869, woodcut. 



