354 PROF. EHRENBERG ON ANIMALS OF THE CHALK 
44. Haliomma radians, Ch. M., Greece. 
45. Navicula Didymus, Ch. M., Caltanisetta. 
a Entomon, Ch. M., Greece. 
47, ———— norwegica, Ch. M., Greece. 
48. — quadrifasciata, Ch. M., Greece. 
49. — ventricosa, Ch. M., Oran. 
50. — viridula, Ch. M., Greece. 
51. Peridinium pyrophorum, Flints of the W. Ch., Gravesend, and 
in the North German Plain near Delitzsch. 
52. Striatella arcuata, Ch.M., Oran. 
53. Synedra Ulna, Ch. M., Oran. 
54. Tessella Catena, Ch. M., Caltanisetta. 
55. Triceratium Favus, Ch. M., Greece. 
56. Xanthidium furcatum, Flints of the W. Ch., near (Delitzsch and) 
Gravesend. 
hirsutum, Flints of the W. Ch., near (Delitzsch and) 
Gravesend. 
57. 
Of these 57 species, 30 belong to the undoubted chalk and 
Sicilian marls. The remainder from Oran, Greece (probably 
fgina) and Zante, are it is true not from chalk marls geolo- 
gically determined with equal certainty, but occur with such — 
numerous animals decidedly of the chalk, both calcareous- 
shelled and siliceous-shelled, that even from these species the — 
geognostic character is more firmly established. 
X. Characters and Descriptions of the Genera and Species 
of Animals mentioned. 
Although the number of the new genera and species of mi- 
croscopic organisms has been considerably increased since my — 
last communications, especially by the recent examinations of 
salt water, yet I have not been able to carry the inquiries ne- 
cessary for their description so far as to include them all in this — 
memoir, which, besides, would have too much extended it. I 
have therefore only given the descriptions of the 10 new genera | 
and 42 new species mentioned in the course of this Memoir, _ 
together with the characters of the living animals of 21 forms, ~ 
which hitherto had only been known fossil, and as empty shells. 
The other forms are already contained in my work on the In- 
fusoria, or in the memoir printed last year on the formation of — 
the chalk. 
The 10 new genera and 40 of the new species belong to the 
class Polygastrica; two species belong to already known genera — 
