242 



ZOOLOGY 



SECT. 



on the back by a well-developed movable joint. The notochord was 

 persistent, and the cranium apparently cartilaginous ; the mandible 

 was autostylic. There were composite cutting dental plates. The 



FIG. 864. Protopterus. Skull, shoulder-girdle, and skeleton of fore-limb. AA, articular 

 bone of lower jaw : AF, prse-orbital process ; a and b (on lower jaw), teeth ; b, basal cartilage 

 of pectoral fin ; B, ligamentous band connecting the mandible with the hyoid ; co. ligamentous 

 band connecting the dorsal end of the pectoral arch with the skull ; D, dentary of mandible ; 

 FP. fronto-parietal ; Ht, membranous fenestra perforated by the foramen for the optic nerve 



- 



bones of 



Op. and ( _, 



of the anterior vertebrae ; &. supra-ethmoid bone ; SK, roofing membrane-bones ; SL, enamel 



ridge of tooth ; Tr. trabecula with the openings for the trigeminal and facial nerves ; W W, 



anterior vertebrae coalescent with the skull ; 1, 2, 3, segments of axis of pectoral fin ; *,*, rudi- 



mentary lateral rays of pectoral fin. (From Wiedersheim.) 



VR 



FIG. 865. Coccosteus decipiens. Side view, restored. A, articulation of head with 

 trunk. DB, cartilaginous basals of dorsal fin. DR, cartilaginous radials of dorsal fin. 

 H, haemal arch and spine. MC, mucous canals. N, neural arch and spine. U, median 

 unpaired plate of hinder ventral region. VB, basals of pelvic fin. VR, radials of pelvic 

 fin. (From Dean, after Smith Woodward.) 



pectoral fins are unknown ; the rays of the small pelvic ( VR) were 

 supported on a flattened plate ( VB). 



With some special features of their own the Dipnoi combine 

 characteristics in which they resemble now one, now another, of 



