Kansas Academy of Science. 11 



far found is three inches in diameter, and the largest, twelve inches. Frequently the 

 fingers were found detached from the body ; and in one case two large ones were found near 

 each other, having so grotesque a resemblance to a pair of diminutive human feet that 

 for a time my assistants positively refused to aid me further! The exterior of the 

 Braehinspongia is silicitied, while through the interior characteristic silicious spicules are 

 distributed. Near the center of the base, and opposite the mouth of the cup, is a small 

 papilliform cone, which others have regai'ded as the point by which the sponge was 

 attached to its support. But, in my opinion, this is a hasty conclusion; and I think it can 

 be shown that this basal protuberance is the remnant of a partially absorbed arm. In a 

 specimen of B. Hoveyii (Marsh), having twelve arms, only six of Avhich appear in the 

 figure (see fig. 2), there is evidence that the sponge arms, though constant in their 

 specific numbers, were at intervals liable to alternate absorption and reproduction. The 

 arm, marked A, seems to be the youngest in a series of which the basal coue, marked B, 

 is the retiring member. A more careful study of these curious and highly interesting 

 fossils may serve to throw liglit upon the mysterious laws of spongoidal growth. 



[Fig. 2.] 



DISCREPANCIES BETWEEN THEOEY AND OBSERVATION OF THE 



MOON'S MOTION. 



BY F. W. BARDWELI, . 



In studying recently the question of the moon's irregularities, I discovered nu apparent 

 source of error afi'ecting lunar computations, whose explanation will probably interest 

 many scientists, though of more special value to the astronomer. 



The problem of the moon's motion has been one of the most interesting, though 

 troublesome, in the series which astronomei's have attacked with such success, as one by 

 one the difficulties have been overcome, and the victors received their well-earned honors. 

 Yet it is well known that the difl'erences between the predicted and observed places of 

 the moon are greater than in the case of any other heavenly body, and that these discrep- 

 ancies have excited the special efforts of investigators. 



Thus a comparison of the Washington observations with the American Ephemeris for 

 1870, indicates erroi-s in the predicted right ascension of the moon, extending from 

 ; 0.84to — 0.S7. 



Among the interesting phenomena dependent upon the motions of the moon, huuir- 

 and solar eclipses are conspicuous, and observations of these have naturally been used in 

 the determination of elements or in the verification of theories, and any error pertaining 

 to such observations would serve to introduce error into lunar tables. 



An eclipse of the moon occurs when she passes into the earth's shadow, and the axis 

 or central line of the earth's shadow is usually reckoned as the prolongation of the line 



