43° 



NATURE 



[March 4, 1880 



aspect of the skull, afterwards proved of such importance in 

 determining the affinity of that genus to the recent Dipnoi. 

 Many important original observations and figures were given by 

 him regarding the cranial osteology of Osteolepis and Diploptcrus, 

 as well as of the gigantic Asterolepis. 



■ M'Coy, while engaged in naming and describing the palaeozoic 

 fossils of the Woodwardian Museum at Cambridge, among 

 which were a considerable number of Scottish fossil fish remains, 

 principally from the Old Red Flags of Orkney, published in 

 1848 some account of his work in naming and describing genera 

 and species. It is greatly to be feared that the enormous field 

 over which his other palaeontological researches extended had 

 not afforded him the time and opportunity to acquire the necessary 

 experience in deciphering fish remain', without which the liability 

 to error is not only natural but imminent. 



To M'Coy we owe the separation of the true Cephalaspidcz 

 from the other fishes, Pterichihys and Coccosteus, with which 

 Agassiz had associated them, and the establishment of the latter 

 as a group by themselves under the name of Placodermata ; also 

 the term "diphycercal," applied to that form of fish-tail in 

 which the vertebral axis is, as in the heterocercal form, gradually 

 attenuated, but runs straight backwards instead of turning up, 

 and the fin-rays being developed equally, or nearly so, above and 

 below, a more or less rhombic and symmetrical form of caudal fin 

 is produced. 



The diphycercal tail is a mart primitive or embryonic form than 

 the heterocercal, of which the modern homocercal tail is again a 

 further specialisation. That this is the case is evident to any one 

 who will carefully compare a proper series of tails of recent 

 and fossil fishes. Prof. Alexander Agassiz has recently put the 

 matter in a perfectly clear and unmistakable light by showing that 

 the tail in embryo Pleuronectida: is first diphycercal (leptocardial), 

 then heterocercal, and finally assumes the homocercal form of 

 the adult in which the heterocercy becomes to external appear- 

 ance completely obliterated. 



Sir Philip Grey-Egerton, whom we are glad to refer to as a 

 veteran naturalist, still living amongst us, and continuing to 

 take the warmest interest in the progress of the science to which 

 he has himself contributed so much, has not in his writings sought 

 to alter the classification of Agassiz save in one or two points of 

 secondary importance. He has busied himself with the descrip- 

 tion of new genera and species, so largely supplied by his ow n 

 magnificent collection as well as by that of his close personal 

 friend, the Earl of Enniskillen, to whom also the friends of fossil 

 ichthyology owe a lasting debt of gratitude. Although Sir 

 Philip's de-criptions mainly relate to fishes from the newer forma- 

 tions in England, he has also made some important contributions 

 to our know ledge of Scottish forms. In his paper on Pterichihys 

 (1848), written in conjunction with Hugh Miller, he corrected 

 some of the mistakes into which Agassiz had fallen with regard 

 to the arrangement of the plates in that genus. In another com- 

 munication," " On the Nomenclature of the Devonian Fishes," 

 he offered some able criticisms on Prof. M'Coy's work in that 

 department, and added as a supplement a series of interesting 

 extracts from letters by Hugh Miller on the structure of 

 Coccosteus. The tenth decade of the Geological Survey, pub- 

 lished in 1S61, contains also from Sir Philip's pen a description 

 of Tiisticheplerus alatus, one of Mr. Peach'smost interesting dis- 

 coveries in the Old Red Sand-tone of John o' Groats, as well as 

 of several beautiful little Acanthodian fishes, two from Caith- 

 ness, also discovered by Mr. Peach, and others from the grey 

 beds of Forfarshire, brought to light by several industrious For- 

 farshire collectors, among whom were the Rev. Hugh Mitchell, 

 the Rev. Henry Brewster, Mr. Walter M'Nicol, and Mr. Powrie 

 of Reswallie. To Scottish carboniferous ichthyology Sir Philip 

 Grey-Egerton also contributed descriptions of two new selachian 

 species, Ctatacanthus hybodoides and C. nodosus : and his paper 

 on the probable identity of Agassiz's genera, Pleuracanthiu and 

 Diplodtis, is also of equal importance to the investigator of the 

 fossil contents of the Scottish as of the English coal measures. 



A third great era in the history of paleozoic ichthyology may be 

 said to have commenced with the publication of the researches 

 of the distinguished Russian naturalist, Dr. Christian Heinrich 

 Pander. With his first great work, the "Monographic der 

 fossilen Fische des silurischen Systems des russisch-baltischen 

 Gouvernements," published in lS5f>, wc have here nothing to do, 

 save to remark that if the singular little tooth-like bodies, known 

 as "conodonts," be in reality what many at the present day 

 suppose them to be, namely, the teeth of Myxinoid fishes, then 

 we shall have abundant evidence of the prevalence of these lowly 



organised fishes far back in Lower Silurian times. It is his thre. 

 subsequent publications, on the " Placodermi," on the "Cteno. 

 dipterini," and on the " Saurodipterini, &c," appearing respec 

 tively in 1857, 1858, and i860, which attract our attention, 

 dealing as they do with the fishes of the Old Red Sandstone, and 

 very largely with Scottish specimens. Fish remains are of frequent 

 occurrence in the Old Red Sandstone of Russia ; many had been 

 previously described by Eichwald as far back as 1839, as well as by 

 Agassiz in his monograph of the fishes of the Old Red Sandstone. 

 These remains are, however, mostly very fragmentary ; to read them 

 aright, comparison with more entire fishes was necessary, and 

 this want was supplied by the liberality and enthusiasm of a 

 member of the Russian Academ;', Herr von Hamel, who under- 

 took a journey to Scotland, and, having collected a large number 

 of specimens both in Caithness and in Orkney, packed them in 

 barrels, and shipped them off bodily to St. Petersburg. There 

 they were placed at Pander's disposal for description, and the 

 results are embodied in the three works last quoted. The main 

 feature in Pander's work was his elucidation of structure, and 

 his clear insight into the fact that only by careful and laborious 

 investigation into the structural features of the skeleton, external 

 and internal, can we hope to determine the natural affinities of 

 fossil fishes. Here his achievements surpassed all that had been 

 previously done in palaeozoic ichthyology. The structure of the 

 Placodermata {Pterichthys, Coceostew, Asterolepis, Heterosteus) is 

 minutely described and illustrated, as also of the Saurodipterini 

 (Osteolepis, Diplopxrus). A like treatment is accorded to 

 Dipterus, for which he institutes the family Ctenodtpterini, in 

 which he also provisionally includes Ceratodus, then only known 

 as a mesozoic fossil, and to Cheirolepis, which he also erects into 

 a distinct family, fully corroborating the views of Hugh Miller 

 and of Giebel as to its place not being among the Acanthodei, as 

 Agassiz had imagined, as well as indicating that he was not 

 unaware of its resemblance to Falizoniscus. The singularly 

 beautiful and complicated microscopic structure of the Old Red 

 Sandstone teeth, so well known as Dendrodus, Lamnodus, &c, 

 is minutely described and magnificently delineated. 



From his elaborate and truly scientific researches, Pander 

 derived one interesting generalisation, which presently rose to 

 extreme importance. Johannes Miiller had loig before shown 

 that the recent Lepidosteus and Folypterus, classed together by 

 Agassiz in one family, that of the so-called Sauroidei, were 

 representatives of totally distinct groups of Ganoids; but among 

 all the fossil fishes of the order, he could for Polrpterus find no 

 ally. Pander, however, pointed nut tint, far irom Potypteius 

 having no ally in past ages, it is to it rather than to Lepidosteus 

 that the affinities of many of the Old Red Sandstone Ganoids 

 point, and more especially those of the group known as Sauro- 

 dipterini. 



In 185S Huxley published observations on the genera Cepha- 

 laspis and Pleraspis, having in the previous year described the 

 new genera Glyptelcemus and Phaneropleuron, with observations 

 on the genus Holop'yehius. In 1S61 his " Essay on the Syste- 

 matic Arrangement of the Fishes of the Devonian Epoch * 

 appeared, in which the whole subject of the classification of the 

 Ganoids, and especially of those of the Old Red Sandstone was 

 discussed. 



Pander noticed the fact that many of the Old Red Sandstone 

 Ganoids were more allied to Polypterus than to Lepidosteus. 

 Huxley, proceeding farther in the same direction, instituted the 

 sub-order Crosso/terygid.e, of which Polyp'erusajaA Catamoichthys 

 are the sole living representatives, but which in palteozoic times 

 included an extensive assemblage of forms, collectively equivalent 

 to Agassiz's Caiacanthi and Saurodipterini. The heterogeneous 

 nature of Agassiz's " Calacanthi" was pointed out, and the term 

 very properly limited to the peculiar genera Caiaeanthus, Uiuhna, 

 Ilclophagus, and Afacropoma, none of which are, however, found 

 in the Old Red Sandstone. The remaining Agassizian Cfclacanths 

 (Holoptychius, Glyptotepis, &c), were placed in a new family, 

 that of the Clyplodipterini, and here are also included forms both 

 with rounded and rhombic scales. Pander's family of " Dendro- 

 donts" was considered to be probably based on teeth of fishes 

 belonging to the Glyptodipterini. But the Russian author's 

 family of Ctenodtpterini and Agassiz's Saurodipterini ait retained 

 and likewise placed in the Crossopterygian suborder, which 

 lastly includes also the fhaneropleurmi, constituted by the 

 singular genus Phaneropleuron. 



The next important point in Prof. Huxley's "Essay" is the 

 attention which he drew to the singular ties which connect the 

 recent genus Lepidosiren (the Australian Ceratodus being at that 



