18 



BRITISH FOSSILS. 



But Undina has two dorsal fins, each supported by but a single, 

 very peculiarly shaped, interspinous bone ; it has a large caudal fin, 

 whose rays are supported by interspinous bones, and which is divided 

 into two equal lobes by the unossified spinal column ; the latter 

 extending beyond the caudal fin as a tufted appendage, or second 

 caudal, provided with very short fin rays. There is a single anal 

 fin ; the pectoral and ventral fins are well developed and obtusely 

 lobate; the pelvic bones are remarkably large, and are united 

 together by transverse branches, which extend from the posterior 

 extremities of each and meet in the middle line ; there are no dorsal 

 ribs and no proper branchiostegal rays, but instead of them, two 

 broad principal jugular plates. Finally, the scales, large, thin 

 and cycloid, are ornamented with elongated splashes and dots of 

 enamel. On the other hand, " Coelacanthus" Munsteri exhibits no 

 one of the positive characters here enumerated, while it has- ribs 

 attached throughout the dorsal region ; in fact, I am inclined to 

 consider it the type of a new genus allied to Phaneropleuron. 



I have seen no specimens of the other species of Coelacanthus 

 enumerated by Agassiz^ and I. can therefore say nothing about 

 them. But Coelacanthus caudalis (Egerton) is a true Coelacanth, 

 as I have convinced myself by examination of the specimen, to 

 wliich the figure in. King's " Permian Fossils " does not quite do 

 justice. 



As the case stands, then, it appears that there is no evidence that 

 the supposed distinction between Coelacanthus and Undina really 

 obtains ; while, on the other hand, a recent careful comparison of 

 well-preserved specimens of Undina and of Macropoma has con- 

 vinced me that these two genera are not much less closely allied. 



Restoration of Macropdmcc. 



