4 WATSON & DAY, Notes on some Paheozoic Fishes. 



from the classical locality, in the Manchester Museum. 

 Many of these are well preserved and although none 

 is complete, they supplement one another so as to 

 give clear information about the whole of the external 

 surface of the skull except in the premaxillary and 

 narial region. 



As these skulls are not seriously crushed, we have con- 

 siderable certainty of their original shape, Holoptychius 

 had a body nearly circular in section at the pectoral girdle. 

 The head is very short, the orbits far forward and mainly 

 laterally directed. The dorsal profile does not form a 

 uniform curve but rises somewhat abruptly a short distance 

 behind the orbits, the anterior part of the head being in 

 consequence dorso-ventrally flattened. 



The general structure will be best understood from 

 the restorations {Fig. i) which have been drawn with 

 great care and are projections one from the other. At the 

 extreme back of the skull, in the mid-dorsal line, is a large 

 bone which corresponds with the two post-parietals which 

 are so constant a feature of early Amphibian and Reptilian 

 skulls. We propose to call this bone the post-parietal. 

 The post-parietal is bounded on each side and is in fact 

 overlapped to a large extent by the tabulars which are 

 large dermal bones ornamented with a slightly impressed 

 sculpture of ridges and grooves. In front of this trans- 

 verse row of three bones lie the parietals, which meet 

 one another in median suture, and together form a large 

 six-sided area on the top of the head. Each articulates 

 with five other bones in addition to its fellow. The lateral 

 margin from the tabular forward, articulates by a rather 

 close suture with a small oval bone which we intend to call 

 the " supratemporal " because it is obviously homologous 

 with the bone which has commonly borne that name 

 in Stegocephalia." : In advance of the "supratemporal" 



