48 



of Dr. Giinther* and Professor Huxley,+ who have published 

 exliaustive memoirs on this subject. 



Two species of living Ceratodonts are recognised, one named 

 after its discoverer, the Hon. William Foster, Ceratodus Fosteri, 

 and Ceratodus miolejns, distinguishable only by its smaller and less 

 ornate scales. These fish, known locally as " flat-heads," inhabit 

 the fresh and brackish waters of the Queensland rivers, and " at 

 night leave the streams, and go out on the flats, among the reeds 

 and rushes, subject to tidal influence." Dr. Giinther is howevei- 

 of opinion that they do not probably live freely on laud, as the 

 limbs are too flexible and feeble to support the hea\y body, and 

 considers that though they may be occasionally compelled to leave 

 the water, they could not remain long in a lively condition Anthout 

 it. The species, wliich range up to six feet in length and twenty 

 pounds in weight, appear to feed exclusively on the remains of 

 plants, Myrtacete and Grarmma; taken in a decomposing state. 



The body of Ceratodus is covered with large cycloid scales, 

 and the limbs are structurally identical with those of Lepidosiren, 

 but the axis and fringe are more dilated, and the fin scales 

 distinctly visi1)le. The internal skeleton, though of a more cartil- 

 aginous tyi^e, resembles that of the mud fishes, and the skull is 

 partly osseous. The anterior nasal openings are situated under 

 the Hp, in front of the vomerine teeth, Avhile the posterior pair 

 are placed in the ca\-ity of the mouth, a little before the maxillary 

 ones. The dentition is essentially that of Lepidosiren, slightly 

 modified to suit herbivorous diet, being adapted rather for " cutting 

 and crushing " instead of " piercing and cutting." It consists of 

 a pair of vomerine teeth, and two molars in each jaw, thus proving 

 the correctness of the views of Pander and Agassiz, who had 

 assigned that number of dental dates to the fossil forms of the 

 middle geologic ages. The respiratory organs are twofold, as in 

 Lepidosiren, but the gills are more developed in Ceratodiis, and 



* Transactions of the Royal Society 1871. 



+ Proceedings Zoological Society, 1876, Part I. Ceratodus PhilUpsi Aij., 

 ManteU Coll. British Museum, June. 



