9 8 



SCIENCE. 



$20, and one very noted objective for which- the 

 maker asks $60 is offered for $27.20. 



We also notice the production of a i-ioth object- 

 ive of 180° aperture, by a maker of reputation, which 

 is sold at $25. A subscriber recently called at our 

 office and stated that a i-6th by the same maker, 

 also sold at $25, divided the 19th band of Nobert's 

 plate. 



We mention these facts to show the variations in 

 the present cost of microscope objectives, which must 

 be perplexing to inexperienced purchasers. The reg- 

 ular price of a first-class i-ioth, of 180 , is about $85, 

 and it would be interesting to compare the $25 arti- 

 cle and note results ; and it would also be useful to 

 note how the cheaper glasses perform their work, as 

 compared one with another. 



As any expression of opinion on the merits of these 

 objectives would be useless, without they were person- 

 ally tested by us, we refrain from offering any advice 

 on the subject. Microscope objectives are not struck 

 in a die like medals, but are the result of manual 

 operation, in which the individuality of the artist may 

 be recognized and developed. In art the relative 

 merits of the master are appreciated by the connois- 

 seur, and a standard of value established ; the same 

 rule applies to optical instruments when perfection of 

 work is aimed at. When Professor Asaph Hall dis- 

 covered the satellites of Mars, it was necessary to have 

 a telescope which would show an object six miles in 

 diameter at a distance of 35,000,000 miles; when 

 called upon to perform this feat, Clark's 32-inch ob- 

 jective responded in a manner which enabled Pro- 

 fessor Hall to make one of the most important of 

 recent astronomical discoveries. To appreciate this 

 performance of the Washington telescope, we may 

 state that it was equivalent to a person stationed at 

 New York seeing an object at Boston which was two 

 inches in diameter. 



Such is the class of work we desire to find in mi- 

 croscopic objectives ; probably there are only one 

 or two men in this country able to produce it ; but it 

 is difficult to speculate as to what the future may 

 bring forth. 



WALKER PRIZES IN NATURAL HISTORY. 



The Boston Society of Natural History offers a first 

 firize of $60 to $100, and a second of $50, for the best 

 memoirs, in English, on the following subjects : For 

 1 88 1 , The Evidences of the Extension of Tertiary De- 

 posits seaward along the cost of Massachusetts ; for 1 882, 

 The Occutrence, Microscopic Structure, and use of North 

 American Fibre-plants (treating especially of the fibres 

 employed by the native races); for 1883, Original Un- 

 published Investigations respecting the Life-History of 

 any Animal. Prizes will not be awarded unless the 

 papers are deemed of adequate merit. 



THE ODONTORNITHES. 



EXTINCT TOOTHED BIRDS OF NORTH AMERICA. 



We merely desire in this place to acknowledge the re- 

 ceipt of the monograph, on the Odo7itornithes, an extinct 

 order of toothed birds of North America, prepared by Pro- 

 fessor O.C. Marsh, and published by order of the United 

 States Government. 



A review of this work is now in course of preparation 

 by one well able to present Professor Marsh's discoveries 

 in all their integrity, and we propose to publish the same 

 with illustrations, which will convey to the readers of 

 "Science" a fair estimate of the value of this work, 

 which is considered by many to be one of the most im- 

 portant contributions to science, issued by the National 

 Government at Washington. 



Reserving our review of Professor Marsh's mono- 

 graph for a future occasion, we now offer his own expla- 

 nation regarding the work, as conveyed in a few intro- 

 ductory remarks: 



" The remains of birds are among the rarest of fossils, 

 and very few have been discovered except in the more 

 recent formation. According to present evidence, the 

 oldest known birds were imbedded in the Jurassic de- 

 posits of Europe, which have yielded three individuals 

 belonging to the genus Arch/xopteryx, so well preserved 

 that the more important characters can be determined. 

 The only other remains of birds found in the Mesozoic of 

 the Old World are a few specimens from the Cretaceous 

 of England, which are too fragmentary to throw much 

 light on the extinct forms they tepresent. 



"The earliest traces of birds hitherto found in the 

 strata of this country are from the Cretaceous, although 

 we may confidently predict their discovery in the Jurassic 

 beds, if not at a still lower horizon. There is at present 

 no evidence whatever that any of the three-toed impres- 

 sions in the Triassic, described as the foot prints of birds, 

 were made by birds ; and the proof now seems conclu- 

 sive that nearly all of them are the tracks of Dinosaurian 

 reptiles, bones of which occur in the same deposits. 



" In the Cretaceous beds of the Atlantic coast, and 

 especially in the green-sand region of New Jersey, vari- 

 ous remains of birds have been found and described by 

 the writer. These fossils, although often in excellent 

 preservation, occur mainly as isolated bones, and hence 

 their near affinities have not as yet been determined with 

 certainty. 



" Along the western slope of the Rocky Mountains, 

 and especially on the adjoining plains in Kansas and 

 Colorado, there is a series of Cretaceous strata remark- 

 ably rich in vertebrate fossils. The deposits are all 

 marine, and, away from the mountains, they lie nearly 

 horizontal. They have suffered much from erosion, and 

 are still wasting away, especially along the river valleys. 

 These beds consist mainly of a fine yellow chalk and 

 calcareous shale, both admirably adapted to preserve 

 delicate specimens, and here have been found the extinct 

 birds which form the subject of the present memoir. 



" The geological horizon of the known Odontornithesxs 

 in the Middle Cretaceous and corresponds to the strata 

 named by the writer the " Pteranodon beds." The lat- 

 ter are included in sub-division number three, in Meek 

 and Hayden's section. The accompanying fossils are 

 Mosasauroid reptiles, which are very abundant ; Plesi- 

 osaurs allied to Pliosaurus ; Pterodactyles of the genus 

 Pteranodon ; and many fishes. With these occur 

 Rudistes, and occasionally Ammonites, Belemnites, and 

 various other Cretaceous invertebrates. 



" The first bird fossil discovered in this region was the 

 lower end of the tibia of Hespcrortiis, found by the writer 

 in December, 1870, near the Smo y Hill River in Western 

 Kansas. Specimens belonging to another genus of the 

 Odontornilhes were discovered on the same expedition. 

 The extreme cold, and danger from hostile Indians, ren- 

 dered a careful exploration at that time impossible. 



