204 



NA TURE 



[August 12, 1909 



Panama, which appears to have been previously uii- 

 described. 



The first part of the second volume of the Memoirs of 

 the Indian Museum is devoted to the initial portion of a 

 report, by Dr. N. Annandale, on the fishes talccn by the 

 Bengal fisheries steamer Golden Crown ■ this section, which 

 is illustrated with five plates, dealing with the skates, rays, 

 and sawfishes. In the group of sting-rays and butterfly- 

 rays, new species of the genera Trygon and Urogymnus 

 are described and named, while in the torpedo-rays, in 

 addition to a new species of Narcine, Dr. Annandale pro- 

 poses the unclassical term " Bengalichthys " for a ray 

 distinguished from Astrape by its thickened and fleshy disc, 

 rudimentary pectoral fins, and degenerate eyes. 



A second new genus of rays, Dactylobatus, has recently 

 been proposed by Messrs. B. A. Bean and A. C. Weed 

 in No. 1682 of the Proceedings of the U.S. National 

 Museum for a species of which two examples were taken 

 off South Carolina nearly a quarter of a century ago. 

 The generic name refers to the presence of a finger-like 

 process jutting from the middle of each pectoral fin, which, 

 together with the subcircular form of the disc, distinguishes 

 this handsomely spotted species from the typical rays of 

 the genus Raia. 



In No. 1677 of the publication last quoted Messrs. D. S. 

 Jordan and J. O. Snyder describe, under the name of 

 Coregoniis oregonius, a new " white-fish " from the 

 McKenzie River, Oregon, where it is locally known as 

 the "chisel-mouth Jack." It is an active, prednceous fish 

 about iS inches in length, which takes the fly readily. 



To the June number of the Zoologist Mr. R. EImhir<;t, 

 superintendent of the Marine Biological Station at Mill- 

 port, communicates a note on whelks as cod-food. . Cod, 

 it is well known, feed chiefly on crustaceans, but two 

 cases are on record where large numbers of whelks were 

 taken from the stomachs of these fishes. Now, although 

 these molluscs, generallv with the operculums cut off, are 

 frequentlv used as bait in cod-fishing, the number of 

 whelks with their operculums in the two instances men- 

 tioned indicates that these had not been taken on lines, but 

 devoured in the course of natural feeding. The author 

 is of opinion that cod seize whelks when the foot is pro- 

 truded, and swallow this part alone, rejecting the shell 

 and its contents by means of a vigorous shake. 



In the same issue Mr. L. E. .'\dams gives some addi- 

 tional notes on the flving-fish problem, in the course of 

 which it is suggested that the discrepancy between the 

 accounts of difl'erent observers with regard to the occur- 

 rence of wing-vibration may be due to the " personal 

 equation " in the matter of vision-power. 



PRIMITIVE DIPROTODOyTS. 



A- 



T last, it seems, the true position of Plagiaulax, of 

 the Dorsetshire Purbeck, described by Hugh Falconer 

 in 1857, has been more or less definitelv determined, and 

 this by means of its early Tertiary American relative 

 Ptilodus, of which remains, in a much more satisfactory 

 condition than any hitherto known, have recently been dis- 

 covered in Montana. These are described by Mr. J. \V. 

 Gidley in No. 1689 (vol. xxxvi., pp. 611-26) of the U.S. 

 National Museum Proceedings under the name of P. 

 gracilis. Of late years Plagiaulax and Ptilodus, together 

 with a number of more or less nearly allied types, collec- 

 tively forming the Multituberculata or Allotheria, have been 

 tentatively associated with the Mctatheria on account of a 

 presumed resemblance of their cheek-teeth to those of the 

 platypus. A study of the skull, pelvis, and limb-bones of 

 the American genus has, however, convinced Mr. G'a'ey 

 that this is wrong, and that the Plagiaulacida: (together 

 with the other Multituberculata) are really marsupials. 

 The unequ.al development of the fore and hind limbs, the 

 characters of the incisors, the form of the palate, and the 

 position of the check-teeth indicate, in his opinion, a close, 

 although not ancestral, relationship with the diprotodont 

 marsupials. 



This is practically a confirmation of the original view 



of Falconer, who regarded Plagiaulax as related to Hypsi- 



piymnodon (Potorus). Cope (who was followed by Mr. 



I.ydekker on p. 195 of the fifth volume of the " Catalogue 



NO. 2076, VOL. Si] 



of Fossil Mammalia in the British Museum "J endorsed, in 

 a somewhat modified manner, this opinion, regarding the 

 Multituberculata as primitive diprotodonts presenting some 

 very specialised features. In the course of his investiga- 

 tion Mr. Gidley has been led to conclude that Bolodon of 

 the English Purbeck is inseparable from Plagiaulax, while 

 the American Chirox is identical with Ptilodus. 



The dental formula of Ptilodus is /.[, i.l, /.4, m.'i 

 The lower jaw is attached obliquely to the skull in such 

 a manner that its condyle is raised above the line of the 

 cheek-teeth (thereby doing away with an objection raised 

 by Owen against the herbivorous nature of Plagiaulax), 

 and the greater portion of the large cutting lower pre- 

 molar does not, in consequence, bite against the upper 

 cheek-teeth, which extend considerably in advance of the 

 same. Mr. Gidley's views, especially if the Triassic 

 Microlestes (a name which it has recently been proposed 

 to replace by Thomasia) belong to the same group as 

 Plagiaulax, will considerably modify opinion with regard 

 to the origin and radiation of the diprotodonts. 



PROBLEMS OF AVIATION. 



'X'HE interim report of the Advisory Committee for .'\ero- 

 nautics, which, in his recent speech in the House of 

 Commons, Mr. Haldane promised shortly, has now been 

 published (Cd. 4711). It will be remembered that the 

 duty of the committee is to advise on questions submitted 

 to it by the Government departments to which the work 

 of constructing and experimenting with aeroplanes and 

 dirigibles has been entrusted. This work necessitates, in 

 some cases, experimental research at the National Physical 

 Laboratory. The committee is intended generally to 

 advance the applications of the science of aeronautics by 

 such means as may seem best. It has arranged already 

 for a series of reports as to the present state of know- 

 ledge on the questions which will have to be considered. 

 These reports are to include papers on the following 

 subjects : — Mr. A. Mallock, on general questions to be 

 studied ; Dr. T. E. Stanton, on recent researches on the 

 forces on plane surfaces in a uniform current of air ; Sir 

 G. Greenhill, on stability and on the screw propeller ; Dr. 

 \V. N. Shaw, on wind structure, dealing especially with 

 the phenomena of gusts, and on the variation of wind 

 velocity with height ; Mr. F. W. Lanchester, on petrol 

 motors for aeronautical purposes ; Dr. W. Rosenhain, on 

 light alloys; and the secretary (Mr. F. J. Selby), on exist- 

 ing knowledge on the subject of the accumulation of 

 electrostatic charges on balloons, and the precautions to 

 be adopted to avoid the dangers arising therefrom. 



To make it possible to decide what work should be 

 undertaken first at the National Physical Laboratory, the 

 committee drew up a list of desirable experiments as 

 follows : — 



I. — General Questions in Aerodynamics. 

 (i) Determination of the vertical and horizontal com- 

 ponents of the force on inclined planes in a horizontal 

 current of air, especially for small angles of inclination to 

 the current. 



(2) Determination of surface friction on plates exposed 

 to a current of air. 



(3) Centre of pressure for inclined planes. 



(4) Distribution of pressure on inclined planes. 



(5) Pressure components, distribution of pressure and 

 centre of pressure for curved surfaces of various forms. 



(6) Resistance to motion of bodies of different shapes ; 

 long and short cylinders, &c. 



(7) Combinations of planes; effect on pressure com- 

 ponents of various arrangements of two or more planes. 



II. — Questions Especially Relating to Aeroplanes. 



(8) Resistance components for aeroplane models, 

 (q) Resistance of struts and connections. 



(10) Resistance of different stabilising planes, both 

 horizontal and vertical. 



(11) Problems connected with stability: — (i.) jnathe- 

 matical investigation of stability ; (ii.) the stability of aero 

 curves of different section and of different plan (Turnbull's 

 experiments) ; (iii.) effect of stabilising planes and invcstiga- 



