274 



HARD WICKE'S SCIENCE- G OSSIF. 



tions form the marginal denticles. Non-celluliferous 

 aspect finely granular, faintly striate." * 



At first Mr. Robert Etheridge was disposed to 

 class the species among the genus Polypora with the 

 specific definition of P. pastiilata. Better specimens 

 having been received from Dr. Rankin, of Carluke, 

 by the Messrs. Young, they have been able to give 

 the above characters, together with the generic and 

 specific name. But wisely the authors say : "The 

 generic position of the fossil is uncertain. It is not 

 a Polypora since it is not reticulate. Thaniiiisciis, 

 King, shows a tendency to reticulation ; but the junc- 

 tions are at small angles. Synodadia presents the 

 next step towards the Fcncstdla type. If the gem- 

 muliferous vesicles described by King are essential to 

 his Thainnisciis, this character is wanting in our 

 species, even in the best preserved specimens. Longi- 

 tudinal sections show the cells starting from an 

 imaginary axis, and reaching the surface at various 

 levels ; but the tendency to an arrangement in trans- 

 verse series is apparent. ]Meanwhile, though strongly 

 disposed to regard this fossil as a true Hornera or a 

 member of a closely-allied genus, we think it safer to 

 leave it in the Palreozoic genus T/ianmisais, and to 

 name it TIi. {?) Raiikini, after the gentleman to whom 

 we owe the finest examples." i" 



The testimony of these eminent specialists in con- 

 necting the present with the past, if only by a single 

 species, is of double advantage to the student in the 

 present state of scientific nomenclature. Certain 

 authors attach too great a value to apparently 

 essential characters in a species, so that minute 

 specific nomenclature often prevents a correlation of 

 the ancient types with the recent types of the same 

 genus ; hence I am glad to make a note of any desire 

 on the part of Paleontologists to bring the past his- 

 toric life of animal or vegetable nearer to the present. 

 This desire to bridge over the wide gulf has been 

 followed by Mr. Brady also in his "Monograph of 

 Carboniferous and Permian Foraminifera, " for one 

 species named by him as Trochammijia gordealis is 

 veiy similar to the figure of the same genus and species 

 found among the Arctic Foraminifera of Messrs. 

 Rupert Jones, &c. 



Are the Hornera the real descendants of the sup- 

 posed extinct tribes oi Fencstdla Polypora and Tkaiii' 

 nisciis ? The question is one open to much debate, 

 but one to which I shall return at some future time. 



There are a few other genera belonging to the 

 Carboniferous Polyzoa of which I am unable to 

 speak with any degree of authority. My desire has 

 been to clear the way for intending students living in 

 isolated localities, and I have here merely glanced at 

 a few of the riches without at all exhausting the mine. 

 The genera Archaopora of De Konick, Heinitrypa 

 Hibernica, and Ptilopora of M'Coy, I have left un- 



* "Ann. and Mag. of Nat. Hist.," May 1873. 

 t Ibid. 



touched, because I have not yet satisfied myself of 

 the true value of their descriptions, and because the 

 old work on these special genera will have to undergo 

 severe revision before long. I here indicate their 

 existence, and keen eyes must go to work to discover 

 fresh iiraterial for the revision. 



I have now come to the end of my catalogue of 

 Carboniferous Polyzoa. The task I set myself has 

 been a pleasant one rather than a burthen, and had I 

 not had the opportunity given to me of publishing the 

 results of my investigations, I should have given it up 

 in despair long ago. In my own locality, I have had 

 no specialist to sympathize with me in the work, and 

 the fragments that I have had to work upon have not 

 been the most encouraging as furnishing matter for 

 a special study. But perseverance has made me 

 familiar with generic and siDecific types, so that the 

 merest fragment from any locality is sufficient to in - 

 dicate the presence of the species. This has been 

 one of the chief charms about the study, to build up 

 a type from the merest fragment ; and although I 

 have not given a vast variety of localities, I have 

 endeavoured to indicate the presence of species where- 

 ever they were most abundant. To the student I 

 will say that I should be happy to name any and 

 every specimen sent to me from different localities ; 

 and to my American friends I will gladly avail my- 

 self of this opportunity of asking from them Devonian 

 or other Polyzoa in exchange for Carboniferous 

 species. According to Prof Nicholson, many genera 

 are plentiful in the Devonian strata of Ameiica, 

 though others are more rare. And to those interested 

 in the subject in this country, who desire the con- 

 tinuation of articles similar to these, I shall also be 

 glad to exchange for Polyzoa from all the various 

 formations in which Polyzoa is known, to form a per- 

 centage of the fossils. I shall be glad to receive the 

 material immounted, but with the localities and strata 

 carefully given. 



My sincere thanks are due to all those friends who 

 have so kindly assisted me in these articles. 



ON CERTAIN GENERA OF LIVING FISH, 

 AND THEIR FOSSIL AFFINITIES. 



No. III. 



IN considering the distribution and range of the 

 various families in geological time, Ave find that 

 authenticated remains of sharks, Placodcrms, and 

 Cephalaspids have been obtained from the Lower 

 Ludlow beds of the Upper Silurian rocks of Europe, 

 but in America it is singular that no fossil fishes have 

 as yet been discovered before the Devonian epoch, 

 when the relics of numerous genera occur abundantly, 

 differing, however, from the European forms. This 

 dissimilarity in the fauna is probably owing to the 

 differences existing in the physical geography of the 

 two areas at the time of the deposition of the series. 



