J. W. Davis — On Ccelacanthus Phillipsii. 159 



is observed to extend along the posterior half of the bone, disappear- 

 ing in the anterior half. 



On comparing this form of dentition with that from the Lower 

 Oolites named Pycnodus didymus, Ag. — which is most probably the 

 lower jaw of Mesodon Bucklandi — it will be seen that the Portland 

 fossil is distinguished (i.) by having the inner series of teeth 

 relatively larger, (ii.) by exhibiting part of a supplementary inner 

 row, and (iii.) by displaying the outer small teeth in three series, 

 with half of a fourth series, all very irregularly arranged. Such 

 differences may certainly be regarded as of specific value ; and these 

 characters also appear to separate the present fossil from all other 

 jaws of Mesodon hitherto described. The most nearly related form 

 is Mesodon Nicoleti (Ag.), from the Portlandian of Soleure, Switzer- 

 land. This species, however, is not satisfactorily defined, being 

 apparently founded on an imperfect mandibular ramus with ab- 

 normally developed outer teeth; and if certain specimens in the 

 British Museum, obtained from Soleure and probably referable to 

 M. Nicoleti, are correctly so determined, the specific distinctness of 

 the Swiss form from the English fossil is shown (i.) by the 

 relatively smaller size of its inner teeth, (ii.) by the absence in it 

 of a partial supplementary series inside and of a fourth series 

 outside, and (iii.) by the greater regularity in the arrangement of its 

 three rows of outer teeth. 



Under the circumstances, the Mesodon of the English Portlandian 

 may appropriately receive the name of M. Damoni, in memory of 

 one of the most successful explorers of that formation, who first 

 made known the fossil jaw by publishing a good figure. 



IV. — On Ccelacanthus Phillipsii, Agassiz. 

 By James W. Davis, F.G.S., F.L.S. 

 rpHE late Prof. Louis Agassiz, whilst on a visit to Halifax with 

 X Prof. John Phillips, during the years in which he was pre- 

 paring his " Eecherches sur les Poissons fossiles," identified the 

 caudal extremity of a large species of Coelacanth fish to which he 

 appended the name of Ccelacanthus Plrillipsii in honour of his friend. 

 The specimen is from a large " baum-pot," as the calcareous nodules 

 are locally termed, obtained from the Lower Coal-measures. This 

 specimen was found at the Swan Bank Pit at Halifax, and, so far as 

 I know, is the only one which has been discovered. The surface 

 exposed by splitting the nodule is 0'295 m. diameter, and the part 

 of the fish preserved extends across it ; it consists of the caudal 

 portion of a large individual, which, had it been perfectly preserved, 

 would have been between four and five feet in length. The vertebral 

 axis extended in a straight line across the surface : its constituent 

 parts are not preserved, but the distance between the neural and 

 haemal spines indicates a vertebral column of considerable size and 

 power. Attached to the vertebral column are about thirty rays 

 above, and a similar number below, which will probably indicate 

 the same number of vertebral segments. The first caudal fin is 



