38 WATSON & Day, Notes on some Palceozoic Fishes. 



aspect of the angular which lies outside it is very well 

 shown. On the left side the angular is incompletely 

 represented mainly as an impression, and overlapping the 

 angulars and quite symmetrically disposed at the front 

 end of the head is a small bone which can only be a 

 dentary. 



Cte nodus ? 

 The Manchester Museum contains a large slab show- 

 ing a good deal of the skeleton of a Dipnoan fish from 

 the Jarrow Colliery, Kilkenny. It is a characteristic 

 example of Huxley's Campylopleurou, as usual not show- 

 ing structural details clearly, but of interest because it 

 shows with perfect distinctness the presence of a pair of 

 dentaries not fused in the middle line. Although it 

 cannot be determined the interest of this fact, and the 

 difference which it presents to the condition in Sagenodus, 

 justify us in giving this short description. 



If we arrange in order of age, as we have done in 

 Text-fig. 8, the drawings of the dorsal surface of the skull 

 in known Dipnoan genera we see at first glance that 

 general resemblance between them which has long been 

 known to exist but we find that Diptcrus valenciennesi 

 from the Stromness and Diptcrus platyccphalus from the 

 Thurso horizons, Pentlandia macropterus, Scaumenacia, 

 Phaneropleuron, Sagenodus and Ceratodus, form a series 

 each member of which differs from that which precedes 

 it in a constant way. Each step shows a reduction in 

 the number of bones, and in each this reduction takes 

 place at the anterior end. Dipterus platycephalus differs 

 from Dipterus valenciennesi in the fusion of the posterior 

 row of three plates with that which lies in front of them, 

 and in a narrowing of its anterior part owing to a loss of 

 two plates. Pentlandia macropterus has advanced over 



