Feb, 24, 1876] 



NA TURE 



327 



eminent German mathematician and astronomer Gauss, 

 in Zach's Monatliche Correspondenz, 1800. 



1. From 1800 to 1899 put m = 23, « = 4. 



„ 1900 to 2099 „ w = 24, « = 5. 



2. Divide the given year by tg, and call the remainder a. 



3- ,, » by 4, „ „ b. 



4- j> >» hy 7, „ „ c. 



5. Add m to 19 times a, divide the sum by 30, and call 



the remainder d. 



6. Add together n, twice 3, four times c, and six times 



d, divide the sum by 7, and call the remainder e. 

 Then Easter Sunday is March 22 -\- d ■\- e^ or 



d-\- e - () of April. 

 To apply this rule to the present year, we have — 



1. w = 23 « = 4 



2. For — — remainder is 14 a. 



3. For 



4. For 



remainder is o 



remainder is o 



d. 



For ^3 + ^9 X 14 remainder is 19 



30 



^-^ — — — — — — — - remainder is 6 ... . e. 



6. For 



And Easter Sunday is March 22 + 19 + 6 = March 47 

 or April 16; or 19 + 6— 9 of April = April 16. 

 Note. — The following are the two exceptions to the 

 above rule : — 



1. If Easter Sunday is brought out April 26, we must 

 take April 19. 



2. If Easter Sunday results on April 25 by the rule, 

 the 1 8th must be substituted when the given year, in- 

 creased by one, and then divided by 19, leaves a re- 

 mainder greater than ir. 



PROF. FLOWER'S HUNTERIAN LECTURES 

 UN THE RELATION OF EXTINCT TO EXIST- 

 ING MAMMALIA ^ 



II. 



'X*HE extinct Marsupialia, Edentata, and Ungulata 

 -*■ were treated of fully in the previous course."^ 

 It is only proposed now briefly to recapitulate the prin- 

 cipal results as bearing on the derivative hypothesis, and 

 to call attention to some recent additions to our know- 

 ledge of the past history of these groups. 



The Monotremata, represented only by the Orni- 

 thorhyncus and Echidna of Australia, the lowest and 

 most reptilian of mammals, seem to be the survi- 

 vors of a group of animals of intermediate structure 

 through which the passage from the lower to the 

 higher vertebrates was made. But of this palaeon- 

 tology has hitherto afforded not the slightest proof. Ex- 

 cept some Pleistocene remains of one of the existing 

 genera, no trace of any extinct animal allied to the 

 ^lonotremata, or showing any decidedly intermediate 

 characters between Mammals and the Sauropsida, has 

 ever been found. The earhest known remains of mam- 

 mals — in fact, all those of the Mesozoic period — appear to 

 belong to the Marsupialia, although too little is yet 

 known of their general organisation to pronounce defi- 

 nitely on their affinities. As early as the time of depo- 

 sition of the Purbeck beds, below the Wealden, two very 

 distinct types of dentition prevailed, bearing some resem- 

 blance to those characterising the modem polyprotodont 

 and diprotodont types, the one being mainly carnivorous 



' Abstract of a course of lectures delivered at the Royal College of Sur- 

 geons '"On the Relation of Extinct to Existing Mammalia, with Special 

 Reference to the Den\'auve Hypothesis," in conclusion of the course of 1873. 

 (See Reports in Nature for that year.) Continued firom p. 308. 



- See Abstracts in Natcee, 1873. 



or insectivorous, and the other frugivorous or herbivorous. 

 True Marsupials, allied to the American Ooossums, have 

 been found in the Eocene and Lower Miocene formations 

 of Europe, but not later. Many of the recently dis- 

 covered insectivorous and carnivorous mammals of the 

 North American Eocenes also appear to have been Mar- 

 supials, but the Tertiaries of no part of the world, except 

 the Australian Pleistocenes, have yielded forms allied to 

 the Wombats, Kangaroos, and Phalangers, now so cha- 

 racteristic of the fauna of that land. 



Palaeontology teaches scarcely anything of the past 

 history of the Edentata, an order which might be sup- 

 posed from the diversity in structure and geographical 

 distnbution of the animals now included in it to have 

 occupied a conspicuous position formerly in the fauna of 

 the world. The American gigantic Pleistocene forms, the 

 Megatherium, Glyptodon, and their allies, are of great 

 interest, but they are all closely related to the existing 

 species of the same countries, and their progenitors have 

 hitherto been sought in vain in the earlier formations of 

 the country. Apparently they formed no part of the 

 Eocene or Miocene fauna of the northern part of the 

 Continent. The European Miocene Edentates, Macro- 

 therium and Ancylotheriuin, appear to be more related to 

 the existing Old World forms, but their structure is as 

 yet very imperfectly known. 



The difference between the Perissodactyle and Artio- 

 dactyle Ungulates was fully established in the earliest 

 tertiaries, beyond which we are not able to trace their 

 history. Recent researches of Leidy, Cope, and Marsh 

 have enabled us to form a tolerably connected idea of the 

 history of both these groups in North America. Before 1869 

 not a single Eocene Perissodactyle had been discovered 

 in that country ; it is now known that wtiile the Lophiodons 

 and Palceotheriums flourished in the Old World, similar 

 forms ranged through the sub-tropical forests of the 

 regions in which the stupendous mountain ranges of 

 Western North .\merica have since been elevated. None 

 of these appear to be identical specifically with the 

 European forms, and even the generic indications, being 

 often founded only on very limited portions of the organisa- 

 tion, as a few teeth, must be regarded as provisional. 

 The best kno.vn forms, Hyrachyus and Palceosyops, are 

 respectively Lophiodontoid and Palaeotheroid. Some are 

 allied to the Hyracotherium, one of which, Orohippus, 

 seems to connect that form directly with Atichitheriutn. 

 One form only, Diceratherium, is Rhinocerotic ; it is 

 found in the uppermost Eocene strata of Utah, and gives 

 the earliest indications of this group yet known. It seems 

 to be connected with the lower Eocene Hyrachyus on the 

 one hand, and the Miocene Hyracodon on the other. In 

 the Miocene period, the Perissodactyles attained a great 

 development of form and size, and the groups became 

 more differentiated, and some of them highly specialised. 

 True tapirs do not seem yet to have been met with. 

 The Palccotheroid and Lophiodont forms had nearly, if not 

 quite, died out, but the more horse-like Anchitherium was 

 abundant, and appears to have continued the line from 

 the Eocene Orohippus (which had four toes on the fore 

 foot) to the true horses of the Pliocene period. Rhino- 

 cerotic forms now became ascendant, being represented by 

 Dicerotheritim with a pair of lateral horns on the nasal 

 bones, Hyrcuodon, a very generalised hornless Rhino- 

 ceros, with the complete number of incisor and canine 

 teeth, and several species assigned to the European genus 

 Aceratherium. But the most remarkable of the Miocene 

 Perissodactyles of North America are a number of 

 species of gigantic size, to the first known of which Leidy, 

 in 1853, gave the name of Titanotherium, and of which 

 other, or perhaps the same, forms have been named by 

 Marsh Brontotherium, and by Cope Symborodon. Their 

 head was large and much elongated, as in the rhinoceros ; 

 but they had a pair of stout diverging osseous protube- 

 rances like horn cores on the nasals or anterior part of 



