72 



necessary to determitie its true character. Here also we find the 

 deposit rich in specimens of Biddiilphia Tiiomeyi, Biddulplna 

 elegans and several species of Rhaphoneis. Not only is the de- 

 posit much richer at this depth, but the forms are also far more 

 robust than in the upper strata. Below 550 feet the diatoms be- 

 come fewer and less interesting, until at a depth of 638 feet only 

 a few of the larger species of Coscinodisciis may be found. 



After the well had reached a depth of about 800 feet, a severe 

 storm destroyed the apparatus employed in sinking it, but the 

 boring will probably be resumed, and it is intended to make a 

 complete microscopical examination of the remaining strata. The 

 well will probably reach a depth of 1,150 feet, the first well hav- 

 ing been completed at about that depth. 



In examining the list of species, it will be observed that there 

 are a few fresh w^ater forms. These are not plentiful, but are 

 sufficient to indicate that the deposits were made within the reach 

 of fresh water influences, possibly within or not far from a large 

 estuary. While, as before stated, the similcirity between the spe- 

 cies in this and in the deposits of Maryland and Virginia is re- 

 markable, it is also a curious fact that the characteristic species 

 of the Nottingham, Md, deposit — Heliopelta Ehrenhergii and 

 Craspedodisctis elegans — are conspicuously absent. The pres- 

 ence oi Hydrosera triquetra is also rather interesting, as this is 

 usually supposed to be peculiar to tropical seas. 



The following is a list of the species thus far observed: 



Actinocycltis Ehrenberghy Ralfs, Several varieties. 

 A, interpmictattis, Brightw. Rare. 



A, Ralfsiiy W. Sm. 



ACTINODISCUS Atlanticus, n. sp. Kain and Schultze. 

 Greville, who constituted this genus, described and figured but 

 one species, A. Barbadensis, He gives the following generic 

 characteristics: " Frustules free^ disk-shaped; valves granular 

 with a central nucleus, and numerous (i 5) linear, smooth, rays ex- 

 tending from it to the margin." In this deposit the specimens 

 differ in the following respects from Greville's fissure. The cen- 



tral nucleus is much smaller; the rays extend nearer to the cen- 

 tre of the valve and are either four, five or six in number. Near 

 the circumference each ray has a strong rib extendintr for a short 



