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SCIENTIFIC NEWS. 



[Nov. 2, i8£8. 



view until Lamarck could show him a three-toed horse. 

 The forerunner of Darwin was brought to silence by this 

 demand. But in our days Cuvier might behold the 

 entire pedigree of the horse from the five-toed Eohippus 

 — an animal no larger than a fox— to the three-toed 

 Hipparion, and so on to the modern one-toed horse, all 

 duly displayed in American museums. The Archasop- 

 teryx of Solenhofen (Scientific News, vol. ii., p. 309), 

 with its toothed beak and its long lizard-like tail, is a 

 true primaeval bird, and fills up an important gap in the 

 most significant manner. Recently more and more in- 

 termediate links have been brought to light, and the rocks 

 speak a language convincing to all who will listen. 



In the last few years, Professor H. Credner, of Leip- 

 sig, has published a series of memoirs on the Stego- 

 cephala. In these papers he has made us acquainted with 

 the structure and the development of a group of animals 

 which became extinct millions of years ago, a group 

 whose existence falls in one of the earliest periods of 



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This hole was formerly a puzzle, but its meaning was 

 interpreted last year, since De Graaf and Spencer have 

 shown that in certain lizards there is an eye at the same 

 place in the skull. This eye is certainly no longer used 

 for sight, but it possesses the same complicated structure 

 as other eyes among the vertebrates. This so-called 

 parietal eye seems to have been still active in those 

 ancient newts, for Credner succeeded in showing that the 

 fine scales covering otherwise the entire skull were not 

 developed over the parietal aperture, so that the parietal 

 eye lay exposed— an observation of very high theoretical 

 value. 



The curious scaly coverings of the abdomen can be 

 seen through the ribs, and are fully shown in figure 2, 

 which represents an allied species (Branchiosaimts ambly- 

 stomns) from below. The short ribs afforded no protec- 

 tion to the abdominal organs. Hence the Stegocephala 

 required a strong scale-armour on their lower surface. 

 Credner has succeeded in showing how this armour was 



Branchiosaurus Amblystomus (from below). 



the earth's history, and which comprises the earliest 

 terrestrial, air-breathing vertebrate animals brought forth 

 by our earth. 



In the Plauen Glen, near Dresden, a deposit of lime- 

 stone is being quarried, of small extent and thickness. 

 But it contains fossil newts, varying in length from two 

 to eight inches, and in such numbers that Credner suc- 

 ceeded in obtaining above a thousand specimens. The 

 skeletons of these little creatures lay upon the grey lime- 

 stone in so faultless a state of preservation that they 

 could be submitted to the most minute examination. 

 Ten distinct forms were discovered by Credner, and the 

 accompanying figure (1) shows in natural size one of the 

 most characteristic species, Pelosaitrus laticeps. The 

 broad, roof-formed skull, whence the name of Stego- 

 cephala, " roof-heads," given to the entire group, is the 

 most striking feature. The body is compact, the tail 

 short, and the limbs well-developed. In the front of the 

 head we see the two nostrils, then the orbits of the eyes, 

 protected by a ring of bony plates, and, finally, a hole in 

 the middle of the skull, between the two parietal bones. 



gradually developed during the growth of the animal. 

 It first appears over the region of the heart, then it 

 spreads down over— or rather under — the abdomen, as 

 in figure 1, and lastly, as in figure 2, it covers the lower 

 side of the four extremities and of the tail. As the 

 possession of this scale-armour is characteristic of all the 

 earlier amphibia in contradistinction to those of more 

 recent periods and of the present, the former are 

 known as " scale-amphibia." 



A much more important fact was elicited on the study 

 of the younger individuals, i.e., that in youth the stego- 

 cephala breathed by gills, but when mature bj 7 lungs. 

 Their development, therefore, was exactly similar to 

 that of frogs in the present day. The arches of the gills 

 are not easily recognised, but small, conical teeth were 

 attached to them, exactly as it is observed in modern 

 fishes and amphibia. Such elegant rows of teeth are 

 found in almost all young stegocephala, behind the skull, 

 and both sides of the back-bone. The fossils in question 

 rank among the most highly prized treasures of the 

 Leipzig Geological Museum. 



