March 1, 1893.] 



KNOWLEDGE. 



67 



lead on to the still earlier lUy-encrinites {Ejicrinns) of the 

 trias. 



If space permitted there are several other groups of 

 invertebrates which might claim our attention, but we must 

 pass on to the vertebrates. Among the fishes the one 

 which has the gi-eatest claim to the title of a " living 

 fossil " is the aforesaid Australian lung-fish of the rivers of 

 Queensland. As we have mentioned in the article referred 

 to, teeth of fishes allied to the Australian lung-fish have 

 long been known from the secondary rocks, ranging down- 

 wards to the trias, and occurring in Europe, India, Africa, 

 and North America. These teeth were, indeed, first 

 described by Agassiz as far back as the year 1838 ; and 

 the group was believed to be extinct till 1870, when one 

 of the two living forms was discovered. At first, as stated 

 in the same article, it was believed that the latter were 

 generically identical with the fossil, Ci'mtodus, but it has 

 been ascertained recently that there are certain slight 

 diflerences which justify the separation of the living species 

 as a distinct genus. At present we have no decisive 

 evidence of the existence of these fishes between the upper 

 Jurassic of the United States and the pleistocene of Queens- 

 land, so that there is a long gap in their history to be 

 filled up, it may be hoped, by future discoveries. 



The AustraUan lung-fish is, however, but one of three 

 nearly allied genera, of which the other two [Lepidosiren 

 and ProtdpteruK) are each represented by a single species, 

 severally inhabiting the Amazons and the rivers of West 

 Afiica. These three widely separated types are, then, the 

 sole living representatives of an extensive order which was 

 once widely distributed over the globe, and has been slowly 

 waning ever since the pala;ozoic period. The group is 

 one of especial interest, since from some of its extinct 

 representatives it is probable that amphibians, and hence 

 the higher vertebrates, have all been derived. 



Of nearly equal interest with the lung-fishes are the 

 bony pikes (Lepidosteus) of the rivers of North America and 

 the bichir {Pohjpteriif:)' of the Upper Nile and the rivers 

 of Western Africa ; which, together with another West 

 African form {Calnmoichthi/s), are the sole existing repre- 

 sentatives of the mail-clad ganoid fishes so abundant 

 during the secondary period. The African forms are at 

 present unknown in the fossil state, but the bony pikes 

 date from the lower eocene, and thus indicate continuity 

 with the extinct secondary types. 



Another living fossil among fishes is the well-known 

 Port Jackson shark {Ci'stracioii), the last survivor of a 

 genus ranging in the secondary rocks of Europe down to 

 the Kimeridge clay ; and also the sole living member of a 

 vast group of sharks characterized by the pavement ol 

 crushing teeth withwhich the mouthiscovcred. Asremarked 

 long since by Dean Buckland, cestraciont sharks lived side 

 by side with trigonias in the old Jurassic seas of Europe ; 

 and it is not a little remarkable to find the same comrade- 

 ship still kept up on the distant coasts of Australia. 



Quite recently another link connecting the present 

 fauna of Australia with that of secondary Europe has been 

 discovered. For a considerable time a peculiar group of 

 herrings (Diplomystiis), characterized by having a row of 

 scutes on the back resembling those found in other types 

 on the opposite aspect of the body, have been known from 

 cretaceous and early tertiary rocks, their range including 

 Brazil, Wyoming, the Isle of Wight, and the Lebanon. 

 Till the other day, these doubly-armoured herrings were 

 considered to be totally extinct, but now, lo and behold ! 

 they have turned up alive in certain rivers of New South 

 Wales. 



* Figured in Knowledge for September, 1892, p. 173. 



Among amphibians, the creature which seems best 

 entitled to be called a "living fossil" is the giant 

 salamai Air(C!;ii'iol'iti)i(iivs) of Japan, since, together with a 

 smaller North American kind, it is the representative of a 

 genus once common in Europe during the middle portion 

 of the tertiary period. Indeed, our first knowledge of the 

 group was derived from a fossil specimen of one of these 

 salamanders frcm the Continent, described in the year 

 172G under the title of Jiotno ililurii testis, in the belief that 

 it was a human skeleton ! 



Passing on to the reptilian class, we have to notice that 

 in the year 1842 the late Sir E. Owen described from the 

 triassic rocks of Shropshire the remains of a small lizard- 

 like reptile (lllijivchcsinn tis), difl'ering from all living forms 

 in the structure of its skull, of which the jaws teiminated 

 in a peculiar beak. Eleven years previously the late 

 Dr. Gray had, however, applied the name Sii/wvodon to a 

 then very imperfectly known living reptile frcm New 

 Zealand ; which when fully described by Dr. Giinther in 

 1867 turned out to be very closely related to the triassic 

 Bl.ijnrliofdunix. Although externally somewhat like a 

 lizard, but with a dit^'erent kind of skin, the tuatara, as 

 the New Zealand reptile is called, d)tlers entirely in the 

 structure of its shell and skeleton in general from the 

 true lizards, and comes much closer in these respects to 

 crocodiles and toitoises. Subsequent researches have 

 brought to light the existence of the remains of a large 

 number of more or less nearly allied reptiles in the 

 secondary rocks oi Europe and other parts of the world. 

 Accordingly the tuatara, although not generically identical 

 with any one of these extinct foims, has every right to 

 be regarded as a "living fossil"; while it enjoys the 

 further distinction of being, with the exception of the 

 lancelet, the only vertebrate animal which can be definitely 

 regarded as the sole living representative of a distinct 

 order. 



Since birds have no species with any very great claim to 

 be mentioned here, we pass on to mammals, of which our 

 notice must necessarily be brief. In a previous article, ^ 

 it has been stated that certain remarkable secondary 

 European and Amciican mamnjals appear lo be related to 

 the egg-Jaying mammals of Australia and New Guinea ; 

 and we may, therefore, assume that the latter, as their 

 structure indicates, are very ancient types, although their 

 direct ancestors have not yet been discovered. The banded 

 anteater {Miiiiiiriol>h(s) and the bandicoots {renimrhs) of 

 Australia seem to be the nearest relatives of another great 

 group of secondary mammals, and are therefore probably 

 some of the oldest types with which we are yet acquainted, 

 although here again their exact genealogy is at present 

 unknown. No other groups ot living mammals are yet 

 definitely known to have existed before the tertiary pericd, 

 and the pedigree of the class in general is consequently 

 brief as compared with that of many of the animals dis- 

 cussed above. The opossums (liidelphi/s) are, however 

 perhaps those mammals best entitled among the tertiary 

 groups to the appellation of "living fossils," as they have 

 existed without generic modification since the periodof the 

 eocene, and have now entirely vanished from their old 

 European haunts to maintain an existence in America, 

 where they are mainly characteristic of the southern half 

 of the continent. Although the insectivores and the lemurs 

 (as mentioned in our article in the January number of 

 Knowledge) are evidently primitive types, but few of their 

 existing genera date far back in the tertiary period, while in 

 the latter group, not a single existing genus is known before 



t KxowiEDGE, IfoTevuber, 1892, pp. 214, 215. 



