70 



KNOWLEDGE, 



[March 2, 1896. 



of tilt basal joint is here prolonged into a spur projecting 

 towards the middle line of the body ; the two branches 

 are long and slender, and the outer one bears a row of 

 bristles. 



Fig. 5. — Under siu-t'acc of a specimen of A.\nj>hus megistos, show- 

 ing the limbs. (After Waloott.) H, hypostoine. 



In the head (Fig. 6) the basal joint is more strongly 

 developed, and the spur is modified to form a jaw working 

 against the corresponding part of the limb on the other 

 side of the body. At the same time the two branches of 

 the limb become smaller and weaker. 



As we trace the limbs backwards, on the other hand, 

 we find that the spur of the basal joint becomes shorter ; 

 and the segments of the inner branch, instead of remaining 

 cylindrical, become broad and flat. The whole limb, in 

 fact, is adapted for swimming rather than for any other 

 purpose. 



Hitherto no trace of the spiral gills described by Walcott 



has been discovered in 

 these specimens. But it 

 must be remembered 

 that Walcott's sections 

 belonged to quite a difl'er- 

 ent genus of trilobites. 

 Allowing for this and for 

 the great difBculties with 

 which he had to contend, 

 it is gratifying to find 

 that his careful and pains- 

 taking researches led him 

 so nearly to the truth. 

 There can be little doubt 

 that the genera examined 

 by him {Calymene and Ccrauni.s) bore antenna, although 

 he did not discover them. Indeed, Walcott himself now 

 believes that he has found a trace of autenn® in some of 

 his sections. It is probable, too, that the appendages of 

 the tail of Cahjmene may have been flattened, but this 

 must reiiiain doubtful lor the present. 



Fig. 6. — Under side of iiead of 

 Triarthrus, sliowing t)ie antenna- 

 and organs of the month. (After 

 Beecher.) 



We may heartily congratulate the American palnconto- 

 logists upon th(! results of their long-continued labours ; 

 but is it too much to hope that l''juropo may some nay join 

 in these researclies '.' Not a single specimen of a trilobite 

 showing appendages has yet been discovered except in 

 America. Surely a diligent .searcli among the least altered 

 of our older rocks might meet with its reward. 



THE FACE OF THE SKY FOR MARCH. 



By IIeriiert Sadler, F.E.A.S. 



SUNSPOTS and faculjB are evidently decreasing in 

 number and size, but should be observed whenever 

 the Sun is visible. Conveniently observable 

 minima of Algol occur at Oh. .'J()m. p.m. on the 

 20th and at Gh. 15m. p.m. on the 23rd. 

 Mercury is a morning star, but, in spite of his attaining 

 his greatest western elongation (S?}") on the 5th, he rises 

 so soon before the Sun that he is by no means well 

 situated for observation. We give an ephemeris of him for 

 the first third of the month ; after that he approaches the 

 Sun too closely to be visible. On the 1st he rises at 

 5h. 51m. A.M., or about one hour before tiie Sun, with a 

 southern declination of 10' 12', and an apparent diameter 

 of 7i", just one-half of the disc being Uluminated. On 

 the 6th he rises at 5h. 17m. a.m., or 50m. before the Sun, 

 with a southern declination of 15° 31', and an apparent 

 diameter of 7", tVo'-lis o^ '■^^ disc being illuminated. On 

 the 11th he rises at 5h. 14m. a.m., or 41m. before the Sun, 

 with a southern declination of 14° 14', and an apparent 

 diameter of 6V', y'g'oths of the disc being illuminated. 

 While visible he describes a direct path in Capricornus to 

 the borders of Aquarius. 



Venus is a morning star, but is rapidly getthig lost in 

 the Sun's rays. In her case, also, we only give an 

 ephemeris for the first third of the month. (Dn the 1st 

 she rises at 5h. 38m. a.m., or Ih. 10m. before the Sun, 

 with a southern declination of 18° 4', and an apparent 

 diameter of 12f", /g^ths of the disc being illuminated. 

 On the 11th she rises at 5h. 30m. a.m., or 55m. before the 

 Sun, with a southern declination of 14° 54', and an 

 apparent diameter of 12^", xoo*''^^ o^ '^^ disc being 

 illuminated. While visible she describes a direct path in 

 Capricornus, being near 5 Capricorni on the 3rd. 



Mars is at present an object of no interest whatever to 

 the amateur, and Uranus rises so late that we defer an 

 ephemeris of him until next month. 



Jupiter is still a splendid object, both in the evening and 

 morning sky. On the 1st he sets at 5h. 32m., or Ih. 16m. 

 before sunrise, with a northern declination of 20° 52', and 

 an apparent equatorial diameter of 44'4 ". On the 11th 

 he rises at Oh. 47m. p.m., with a northern declination of 

 21° 0', and an apparent equatorial diameter of 43|". On 

 the 21st he sets at 4h. 10m. a.m., or lb. 51m. before sunrise, 

 with a northern declination of 21° 3', and an apparent 

 equatorial diameter of 420". On the 30th he rises at 

 llh. 80m. a.m., and sets at 3h. 31m. am. on the 31st, 

 with a northern declination of 21° 2', and an apparent 

 equatorial diameter of 40f ''. He describes a short retro- 

 grade path in Cancer till the 21st, when he begins to 

 retrace his steps. The following phenomena of the satellites 

 occur before midnight on the days named, while the planet 

 is more than 8° above and the Sun 8° below the horizon : 

 On the 1st a transit ingress of the third satellite at 

 6h. 49m. P.M., of its shadow at lOh. 13m. p.m. ; a transit 

 egress of the satellite itself at lOh. 27m. p.m., an occulta- 

 tion disappearance of the first satellite at llh. 26m. p.m. 

 On the 2nd a transit egress of the fourth satellite at 



