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HARDWICKE'S SCIEN CE-GO S SIP. 



[May 1, 1S69. 



which these Entomostraca occur at Bradford is also 

 very full of fish remains, for the most part in a very 

 fragmentary state ; and the fact of fish remains being 

 found in this state generally is held by several 

 geologists to be caused by the presence of these En- 

 tomostraca. In the shale above a small seam of 

 coal in this locality, locally known as the Lit tie Mine, 

 but better known to geologists as the Lower Eoot 

 Coal-mine in the Ganister series, are found fish 

 remains identical with some of those found in 

 Northumberland. I have cut transparent sections 

 of Coprolites from this Lower Eoot coal, and they 

 show long and cross sections of Ganacrodus hastula 

 (Owen), showing the beautiful point, which seems 

 to be the only part tipped with enamel. Cross sec- 

 tions of teeth that are scarcely visible to the naked 

 eye are also shown in these Coprolites. The dentine 

 of the tooth, with the pulp cavity in the centre is 

 shown as distinct as if the section was from one of 

 the large Sauroid-fiskes (of course it requires the 

 higher power of the microscope to see this). In 

 the same Coprolite are also shown sections of scales 

 cut in various directions, as well as fragments of 

 bones, &c. Another Coprolite I have found in the 

 shale above this little coal-seam shows in a trans- 

 parent section almost an entire mass of very small 

 scales, cut in almost every direction : they show the 

 markings on the scales most splendidly.— John 

 Bidterworth. 



What is a Geological Eokmation ? — At one 

 time I could have given a tolerably definite answer 

 to the above question, but if we are to accept the 

 views suggested to Dr. Carpenter and Dr. Wyville 

 Thomson, by the results of their late deep-sea 

 dredging, it will not be easy to say what constitutes 

 a geological formation. I considered that I under- 

 stood the matter when I believed that such a for- 

 mation was a bed, or series of beds, that had a 

 definite stratigraphical relation to other series of 

 rocks, and was when fossiliferous marked by a dis- 

 tinctive fauna or flora of its own. We further 

 fancied that such formations were not originated 

 contemporaneously, but succeeded each other in 

 time, from the "Laurentian" of an epoch vastly 

 remote, to the "Eskers," "raised beaches," and 

 " valley gravels," of " Postpliocene " date. Drs. 

 Carpenter and Thomson put forth a theory that sur- 

 prises me as much by its slender foundation as by 

 its novelty. They say (speaking of the calcareous 

 mud that they found on the floor of the North 

 Atlantic, off the Earoe Islands), " This mud being 

 not merely a chalk formation, but the chalk for- 

 mation, so that we may he said to he still living in 

 the Cretaceous epoch?'' {Vide Report on Dredging 

 in last number of Proceedings of Royal Society.) 

 On reading the above, I looked with some eagerness 

 for the grounds on which such a startling announce- 

 ment was made, and I must confess that they are not 



to my mind at all convincing. Some stress is evi 

 dently laid on the physical character of this sea- 

 bottom : it is a viscid mud, that, like our Cretaceous 

 rocks, is mainly composed of calcareous exuviae of 

 marine organisms. Then there is an abundance of 

 siliceous sponges, but it is not shown that any of 

 these are identical with Cretaceous sponges. What 

 appears to be the strongest part of the case I will 

 give in the words of Dr. Carpenter. He says : — 

 " Thus among molluscs we have two Terehratu- 

 lidfp, of which one at least, Terebrdtula caputser- 

 ■pentis, may be certainly identified with a Cretaceous 

 species, whilst the second, Waldheimia cranium, 

 may be fairly regarded as representing, if not lineally 

 descended from, another of the types of that family 

 so abundantly represented in the chalk. Among 

 Echinoderms we have the little Rhizocrinus, that 

 carries us back to the Apiocrinitc tribe, which 

 flourished in the Oolitic period, and was, until 

 lately, supposed to have had its last representative 

 in the Bourgetticrinus of the chalk, to which the 

 Rhizocrinus has many points of remarkable corre- 

 spondence. Among Zoophytes, the Oculina we met 

 with in a living state seems generically allied to a 

 cretaceous type (0. explanata of Michelin)." If 

 evidence like the above will justify us in considering 

 that the Cretaceous epoch is still unexpired, what 

 formation can we truly say is complete ? But the 

 argument is not sufficiently convincing to cause us 

 to make such a huge "rectification" of our ancient 

 boundaries. Geologists know well that there arc 

 no entire life-breaks, some species live on and pass 

 up from one formation to another more recent ; so 

 that if the T. caput -serpentis be the T. striata of the 

 chalk (which I doubt), it would not prove anything. 

 The Pear Encrinite (Rhizocrinus), the Madrepore 

 coral (Oculina), and the Wuldheimia are not speci- 

 fically identical with Cretaceous species, but only 

 " generically allied." Generic alliance of the fauna 

 will not, however, suffice to unite two beds in the 

 one formation ; nor will it even when combined 

 with similarity of lithological character. If it were 

 otherwise, then the blue clay of Belfast Bay, which 

 lithologically resembles the lias clay very closely, 

 might be said to be a continuation of the Liassic 

 series. We have here, too, the Comatula, repre- 

 senting the Pentacrimis of the lias, with oysters, 

 and a score or more of others that are " generically 

 allied " to Liassic types. Further, our Solaster and 

 Ophiocoma closely represent forms of star-fishes 

 (Lepiduster and Protaster) that lived in Silurian 

 times. The same may be said of several genera of 

 living Mollusca, so that if we accept the statement 

 I have been commenting on, some other savans may 

 show that we are actually living in Silurian times. 

 Geology would have to be freed from all our pre- 

 vious ideas regarding the sequence of strata, and 

 we would have to answer anew the question, What 

 is a geological formation ? —S. A. Stewart, Belfast. 



