414 PABENTAL CAKE AMONG FRESH- WATER FISHES. 



The CeratodontkU are a family of ancient lineage and, indeed, 

 were for a long time supposed to have died out in the early Mesozoic 

 period. 



In 1870, however, "the startling intelligence was published that a 

 living species of Ceratodus had been discovered in Queensland. 

 The skepticism Avith Avhich this announcement was at first received 

 was soon quieted by detailed examinations, comparisons, and descrip- 

 tions. It was later admitted that the living fish was indeed different 

 generically from any earl}^ extinct species known (and named Neo- 

 cerafodys), but it was nearly related to the ancient members of the 

 family. The family is of even greater interest and importance than 

 the Lepidosirenids, but as the species is not a special caretaker of 

 eggs or young, no notice of it is called for here and we pass on at 

 once to the Lepidosirenids. 



THE LEPIDOSIRENIDS IN GENERAL. 



The Lepidosirenids are much further removed from the ancient 

 lung fishes than the Ceratodontids, and so far no extinct members 

 have been discovered. 



The shape is anguilliform and the paired fins are reduced to little 

 more than the stems, the rays being atrophied or lost. The teeth in 

 number are the same as in most of the order, a pair of palatine and 

 pair of vomerine teeth above and in opposition a corresponding pair 

 of molar teeth in the lower jaw. The pneumatocfjele is manifest in 

 the form of a pair of entirely distinct lungs. 



In the living animals, according to Professor Lankester, the body 

 is covered by '* soft vascular connective tissue, in addition to a well- 

 developed epithelium," and consequently " no scales at all or parts 

 of scales are visible on the surface of the body of a fresh or well-pre- 

 served specimen." The scale-like areas which are "" marked out on 

 the surface of the body " are in fact lozenge-shaped areas " outlined 

 by the greater abundance along their margins of the large branching 

 pigment cells of the connective tissue, which overlies as a uniform and 

 continuously flat layer the subjacent scales." 



Two genera of Lepidosirenids are represented by living species — in 

 Africa Protopterus, with three known species, and in South America, 

 Lepidosiren with one. Superficially the}^ resemble each other so 

 much that some have referred both to the same genus, but the ana- 

 tomical differences are numerous and some of them striking. In 

 Lepidosiren there are only four slits between the branchial arches, 

 in Protopterus five; the scapular arch is connected with the cranium 

 in Lepidosiren only by a ligament, but in Protopterus there is an 

 osseous connection by a bone called the " supraclavicle." The body 

 of Lepidosiren is also more slender than in Protopterus, the ventral 

 fins farther back, and the dorsal fin considerably shorter. 



