330 Sketch of the Infusoria of the family Bacillaria. 
perforations, and having at the extremities projecting spines. I 
suspect that these belong to the genus Dictyocha of Ehrenberg, 
several species of which occur at Oran, Caltasinetta, &c.* 
_ Pl. 3, fig. 25, shows a siliceous ring with projecting spines; it 
is possibly a fragment of the preceding. 
Pl. 3, fig. 26, shows a circular ring connected with a concentric 
hexagon by six rays proceeding from the angles of the hexagon. 
The spaces within the hexagon and below the rays are perforations. 
It is possibly another species of Dictyocha. It occurs occasionally 
among fossil infusoria from Richmond and Rappahannock cliffs. 
Pl. 3, fig. 27, shows a curious fragment apparently siliceous, 
having a campanulate form with a projection at the apex, and 
pierced with large holes. Fig. 28 shows an ovoid body perfo- 
rated by similar holes. Of the nature of these curious. fossils, I 
am entirely ignorant. "They occur with the preceding. 
Pl. 3, fig. 29, shows a triangular binary siliceous body, resem- 
bling some of the fluviatile species of Euastrum. The surface is 
covered with minute dots, some of which form lines leading from. 
the centre to the angles. Perhaps this belongs to Ehrenberg’s 
genus T'riceratium, of which species occur fossil at Oran, and 
living in Cuxhaven. | 
“In Pl. 3, figs. 30 to 35 show siliceous bodies which are quite 
abundant with the preceding forms, and which I suspect are spl- 
cule of marine sponges. Many of them show a central perfora- 
tion, like that in the spicule of Spongilla.¢ 
Other interesting forms occur in the infusorial strata of Vir- 
ginia, but the limits of this paper will not allow me to present 
any more of them at present. I have transmitted specimens from 
Richmond to Ehrenberg, and he will doubtless determine to what 
extent the African and American beds agree in their microscopl¢ 
fossils. As the infusorial strata of Virginia belong decidedly “4 
the tertiary epoch, and yet appear to agree remarkably with what 
Ehrenberg considers as chalk marl from Oran, a revision of the 
evidence upon which the siliceous infusorial conglomerates of 
Africa and the south of Europe were referred to the cretaceous 
bigot, © Ae eh Re aS, 
_* Since the above was in type, I have seen Ehrenberg’s figures of several spe- 
cies of tyocha in the Berlin Transactions, and find them to agree the 
‘Shiela alee Wallbided 10. . ; 
oo + Dhav mT alg 3 sy 
= v to beli hat simil siliceous spicule cour in vast quantities 
int external rays of some species of Actinia. en 
te 
