and its Place in the System. 22 3 



group of fishes. The skeleton is notochordal, all its parts 

 having a cartilaginous basis, more or less incompletely covered 

 by thin osseous lamellae. Some of the thickest bones of the 

 skull have a spongeous texture, and there is also a cavity 

 of considerable size in tlie pelvis ; but otherwise the skeleton 

 is composed of solid cartilage (that is, the primordial base of 

 bone) ; and therefore it is scarcely correct to describe the ske- 

 leton of Ceratodus or of Coelacanths as composed of bones 

 " liollow like those of birds." 



The ossifications of the skull may be designated thus : — 



1. Ethmoid. 



2. A pair of frontals separated by a " scleroparietal," which 

 is membranaceous in Lepidosiren. 



3. Basal. The vomer is cartilaginous and tooth-bearing, as 

 in Lejpidosiren and Protopteriis^ in which it has been described 

 as intermaxillary. 



4. A pterygo-palatine on each side of the basal — tooth- 

 bearing, and suturally united witli its fellow. 



5. An OS quadrafiim, represented by an osseous lamella 

 coating the cartilaginous tympanic pedicle, which is provided 

 with a double condyle. 



6. Mandible with an articular and dentary lamella. 



7. A well-developed rhomboid operculum and styliform 

 suboperculum. 



8. Hyoid arch, more complex than in Lepidosiren^ consist- 

 ing of a pair of ccrato-liyals, a basi- and glosso-hyal. 



There are about 68 sets of apophyses, 27 of which bear 

 ribs. The apophyses are most differentiated about tlie middle 

 of the vertebral column ; and towards the end of the trunk the 

 neural portion consists of the following pieces : — 



1. Cartilaginous arch of neurapophysis for the formation of 

 the medullary canal. 



2. Semiossified gable-like portion of the neurapophysis 

 over the ligamentum longitudinale. 



3. Neural spine. 



4. Lower interneural. 



5. Upper interneural, to which the dermo-neurals are at- 

 tached in the same manner as in Protopterus. 



The haemal portion is of very similar construction. 



The fore and hind paddles are supported by a cartilaginous 

 axial skeleton — that is, by a median longitudinal series of 

 joints with lateral divergent articulated branches, each Joint 

 forming the base for a right and left brancli. I have no doubt 

 that the Ganoids of the Devonian epoch with " acutely lobate" 

 fins had the paddles supported by a similar internal skeleton. 

 In Lepidosiren and Protopterus only the jointed axis is per- 



