Contributions to Electricity and Magnetism. 117 
eric name. It will be placed in a natural order immediately after 
Puo.cus. 
Subgenus SpermornHora. 
Eyes, six, in two clusters, oneon 4 
each side of the cephalothorax, thus ~ = ——™~ 
Legs, the first pair longest, then the fourth and second, nearly 
equal, the third pair shortest. Length moderate, slender. 
Lip, wide, triangular. é 
Mazille, tapering towards the point, inclined over the lip. 
Mandibule, short, conical, with very small fangs. 
The characters derived from the trophi, are nearly those of 
Pholcus, but the absence of the two eyes in front of the cephalo- 
thorax, would alone, remove this spider from that subdivision. 
Moreover, the legs, which in Pholcus are excessively long, are here 
of amoderate length. ‘This spider, which is wholly of a pale hue, 
makes its very loose web in dark places, under rubbish. ‘The 
female carries in its mandibles its eggs glued together without 
any silk, until they are hatched. Inhabits Alabama. 
This species, the 137th of my MS. catalogue, is there named 
Spermophora meridionalis. Of the 147 species comprised in this 
catalogue, there are not ten mentioned in European works, besides 
those described by Bose, whose manuscript was never printed.* 
Florence, Ala., ea 2, 1839. 
Arr. XIIL.—Contributions to Electricity and Magnetism.— 
No. IV. On Electro-Dynamic Induction ; by Josern Henry, 
LL. D., Professor of Natural Philosophy in the College of New 
Jersey, Princeton. Read June 19, 1840.7 ze 
MiContinued from p. 243, Vol. xxxvitt, No. 2, of this Journal.) 
‘INTRODUCTION. ¥ 
L. In the course of my last paper, it was stated that t inves- 
tigations which it'detailed were not as complete in so teshadies 
I could wish, and that I hoped to develop them more fully in 
iE eg dee ei cat ee ee 
* A valuable catalogue and description by Prof. Hentz, of the aE of Ara- 
neides found in this country, was published in this Journal, Vol. xx1, p. 100—109, 
t From the Tienes of the American Philosophical Society, Vol. 8, N. e 
* 
# 
