r2.4 



REPORT --1884. 



permanently. However, this seems open (o the same olijection as the precetlin-r 

 theory. ' 



Last come the Astronomical or Periodical theories. A tilt of the eiirtirs a\i, 

 was sug}?ested by lielt, but siifrgested as owinp" to causes whicli are wholly insiiHi- 

 cient. Tiltinpf from astrouomical a<^encies is sliyrlit, thouu'li its action would U. in 

 the direction required. Herschel suj^pfested the lOccentricity tlieorj', but abandoned 

 it. Adhem'ir's Precession theory, as explained by himself, involved an absoliiie 

 fallacy. The celebrated vitiw of Dr. Croll combines the Precession and ]']cceii- 

 tricity theories into one. It; exactly afirees with the Antarctic greater exteussioii 

 of ice, and provides an explanation of iuterglacial warm periods. "J'he great dilli- 

 culty in its way is to see how a mere dill'erence in distribution through the year of 

 an unchanged total beat-receipt can produce consequences so vast. The laws nf 

 radiation explain but a very minute part, the laws of evaporation perhaps ratliir 

 more ; but, so far as can at pre.sent be seen, both together are inadequate. Anotlur 

 .serious objection is that tlie theory seems to require tlie climate of the northern 

 hemisphere to be now in a state of change for the better, of which at present tlieri- 

 appears no evidence. 



Dr. ("roll's elaborate explanations of the reaction of one effect npon aiiothfr- 

 fogs, deflection of currents, and tlie like — liavt^ no special connection with hi^ 

 own theory'. They would act in all cases, and su})port all theories equally. Tlir 

 arguments, if admitted, would only prove that the earth's climates are in a statu ni' 

 highly unstable equilibrium, in which a slight cause may produce an enornioii< 

 change. Nor are his arguments universally admitted. 



In conclusion, Dr. ('roll's theory -seems inadeiiuate : alteration of currents ini.! 

 winds are the most powerful causes suggested hitherto : lurther inve>tigatioiiv 

 ought to be made as to the nature and extent of the last series of changes in the out- 

 lines of the continents of the globe. 



9. On the recent Discover'/ of iieio av/J remitrlcahli' Fiissil FisJn',^ in tic 

 Carhontferous and Devonian Rucks of Ohiu and Indiana. Bij Professor 

 J. S. Newberry, M.D. 



The fishes described by the author consisted of: — ■ 



1. Two new species of Dinicht/ii/s from the Huron Shale (Upper Devonian) nf 

 Northern Ohio. Of these one is consideraldy larger than either of the two gigantic 

 lishes described in the Geological lleport of Ohio under the names of Diiiicliihii< 

 Jlcrzcri and D, Tcrrelli, the cranium liaving a breadth of .'] feet 8 inches. Tbisi- 

 about one-third larger than the largest specimen of Diniclithys before known, and 

 two or three times as large as Asferulepis of Hugh Miller and Heterostens of PaiKler, 

 its congeners. Another is a small species of l)inic/it/ii/s of whicli the dorso-mediaii 

 plate is only 5 inches in breadth and G in length. The mandibles are not nnw 

 than G to 8 inches in length, but are much worn by long use, indicating maturity. 



2. The pavement teeth of a gigantic ray, Arc/tavbatis i/ii/ds, Newb., from th • 

 lower Carboniferous of Indiana ; the largest tooth is over G inclies long bv 4 inclii* 

 wide and one and a half thick. These teeth formed several rows in ilie lunulli 

 above and below. In shape they resembh? t lie teeth of ll'^n modus, but the euninelled 

 surface was strongly ridged to prevent the slijiping of molluscs, Crustacea, kc, 

 which formed the food of the fish. 



3. Diplognathm mirahilis, Newb., a lu'w genus and species in which the man- 

 dibles, set along the anterior portion with conical teeth, diverge at the symphysis 

 forming a fork which carries another row of strongs acute, recurved tee+b. As 

 such a forked jaw would be liable to be ,'^])lit, the rami were united at the sym- 

 physis by a strong ligament, deeply inserted in each bone. This apparatus, 

 admirably adapted for catching slender and slippery fishes, is difl'erent from any- 

 thing hitherto known among vertebrates. 



4. The teeth of .several species of Mijlostoma, Newb., a new genus of fishes, 

 probably allied to_ Dinichthys on the one hand and to C'fenodns on the other, in 

 -which the under jaw was provided with one or more pairs of powerful crusbiii): 



