STETJCTURE OF CERTAIN PALEOZOIC DIPNOI. 187 
remarkable specimen occurring on a slab o£ shale in the Attliey Collection 
has, indeed, retained its original shape, though surrounded by other bones of 
Sagenodus ivhich have all suffered the usual flattening. It should be added 
that the faces of the clavicle identified above as upper-and-iuternal and as 
lower-and-external have, as the figures show, all the character of internal 
and external faces respectively. Miidl described and figured an articular 
area on the broad lower end of the clavicle, and he suggested that the 
two clavicles met each other at an acute angle in this articulation. Well- 
preserved examples, however, show no such articular area, nor would 
they fit together at all exactly by their ends. In all probability they 
were connected, as in Ceratodus, by an interclavicular cartilage. 
We have nothing to add to what has already been published regarding the 
structure of the body, fins, and scales. There is every reason to suppose 
that these parts of Sagenodus are closely reproduced in the existing 
Ceratodus. 
The Species 0/ Sagenodus. 
A glance at the portions of cranial roofs shown in outline in fig. 2, p. 1 65, 
will suggest that they represent more than one species of Sagenodus. At 
least one further species is certainly represented by the zoned and polished 
skull-bones found so abundantly in the Bohemian Graskohle and in some 
numbers also at Newsham [cf. fig. 4. D, p. 168). But there is rarely anything 
distinctive about the teeth in the cases where it is possible to assign them 
with certainty to any particular pattern of skull, and there is little ground 
for attaching the slightest value to most of the specific names founded so 
freely on the teeth. Most parts of the skeleton, and especially perhaps the 
parasphenoids, the separate elements of the lower jaw, and the opercula, 
show varieties of pattern as important as those of the cranial roof and the 
teeth ; and until the different patterns of all these parts have been studied 
and correlated there will be little use in applying specific names to Sagenodus 
at all. Such a study would be extremely difficult on account of the frag- 
mentary nature of the evidence, and it might very possibly result in the 
conclusion that Sagtnodus was, in its sphere of life, a dominant form in such 
a fluid evolutionary stage that it would be for the most part impossible to 
apply to it the ordinary conceptions of a species. 
FritscK s figures of the Cranial Bones of Sagenodus. 
Fritsch's figures are beautifully drawn, and form a valuable atlas of the detached bones of 
Sagenodus, but the fact that so many of them are unidentified detracts from their usefulness. 
Some of these unidentified bones are named in the following list : — 
Plate 71 {Fauna cler Gaskohle, vol. ii. part 2, 1899) : fig. 10, right intertemporal ; fig. 11, 
right nasal. 
Plate 72, fig. 10, left " tabular." 
Plate 74 includes a good selection of different forms of "parietals "; fig. -5, an extreme 
example of the rectangular type. 
