NATURAL SCIENCES OF PUILADELrUIA. 193 



same. He expressed himself to that effect in letters to my father. From Dr. 

 Griffith, Prof. Adams may have received the same imj)ression (sec Vt. Moll.) I 

 am inclined to differ from them, believing the sijccies, though nearly allied, to be 

 quite distinct. Until we receive the true II. fuUyinosa from the South-western 

 States, 1 shall doubt its existence there. Our country has been too little 

 searched, however, to allow us to draw very nicely the lines of geographical 

 distribution. If I am correct in my view of this species, Mr. Say's name will, of 

 course, take precedence over that of Dr. Pfeittcr. 



Helix clausa. The specimens are much more globose than that figured in 

 Am. Conch. The aperture is quite orbicular. 



Helix appressa, hirsuta, inflecta, profunda, auriculata, ligera, solitaria, 

 supprgssa. 



H. patigiata, as fig. in Terr. Moll. iii. pi. sxxix, f. 4. 



H. PUCATA. Like Troosliana, Lea. 



H. FALLAX. The upper denticle on the peristome placed within the aperture, 

 like that of//, vulluona, Gould. 



H. septemvolva. Larfife and small var. of cereolus, Mhtl. 



SucciNEA avara, campestris. Same as figured in Terr. Moll. 



Helicina orbiculata, occulta, (fossil.) 



Pupa pentodon, corticaria, armigera. 



AcHATis.A solida. Morc elongated than that fig. in Terr. Moll. 



November '6d, 1857. 



Vice President Lea in the Chair. 



Mr. Slack remarked, that the specimens of chalcedony and quartz 

 presented by him this evening, had been obtained from a quarry on the 

 left bank of the Nile, whence was procured the limestone used in the 

 erection of the Pyramids. They appear to have been rejected by the 

 workmen when selectino: the lime. 



November 10<7i, 1857. 



Mr. Cassin in the Chair. 



Dr. Morris called the attention of members to an appearance of the eastern hori- 

 zon just before, at and after sunset. On any clear evening, after a warm day, a per- 

 son looking towards the east a few minutes before sunset, will observe a red band 

 of light extending along the whole horizon; above, it is gradually shaded into 

 yellow light, which passes into greenish, and finally into blue, at various distances 

 from the zenith. As the sun decends in the west, these bands of red and yellow 

 light rise in the east, until the red makes an angle of about 15° with the plane 

 of the horizon, leaving a clear dark blue space beneath. The colors are brightest 

 about ten minutes after apparent sunset : after which they gradually fade away. 

 A cloudy or misty state of the atmosphere near the zenith of the observer ob- 

 scures or prevents the occurrence of the phenomenon : but a fog-bank in the 

 horizon does not interfere. In Kaemtz's Meteorology, translated by Walker, page 

 408, the same phenomenon is partially described, but he places the " white or 

 yellow stripe '' between the red and the blue of the horizon, or below the red. 

 I have never seen it anywhere but as above. Kaemtz thinks that the blue is due 

 to the shadow of the earth projected against the eastern sky, while the red 



1857.] 



