STRUCTURE OF CERTAtN PALEOZOIC DIPNOI. 203 
details with great perfection. Other specimens show the cranial roof from 
the visceral surface. 
The cranial roof consists of a series of bones arranged very nearly as in 
Ctenodus, but the three nearly complete examples in Edinburgh differ in' 
details. There is a posterior row of three bones, a median " parietal,'' 
which supports a pair of frontals, and lateral tabulars which are shorter than 
the " parietal " and are continued forward by intertemporals. 
The frontals are separated anteriorly by a small interfrontal, but support 
a pair of nasals in two sj)ecimens and only a single median nasal in the 
skeleton. Finally, in this specimen the skull-roof is completed by a small 
median prenasal with a notched anterior border. 
Fig. 31. 
Uronemus splendens, Traq. Roof of the skull, seen from the ventral surface, x f . 
Fk,., frontal; I.Fn., interfrontal; I.Tem., intertemporal ; Na., nasal; P.O., post-orbital ^ 
Par., parietal ; Sq., " squamosal " ; Tab., " tabular." 
The intertemporal and tabular articulate with a large squamosal, there 
being no evidence of the presence of the two small elements which in most 
Dipnoi appear on the margin of the shield bordering the tabular and 
squamosal. 
The intertemporal is continued forward by a large post-frontal, which 
itself supported another element, which although now lost in every specimen 
cannot have entered the orbital margin. 
Four circumorbital bones are preserved in the skeleton ; probably one more 
was originally present. The three specimens which show that region differ 
considerably in the details of these circumorbitals, which articulate with the 
squamosal and post-frontal. All the bones of the skull-roof bear a crisply- 
marked fine ornament of ridges and pits, which in general radiate from the 
