80 Notice of Memoirs—Dr. Riist’s Cretaceous Radiolaria. 
conical summit with key-shaped grooves for the arms; Triccelo- 
crinus? Leei, with shorter limbs and shallower excavations than 
T. Woodmani, Wachsm. and Springer; and Serpula? devoniana, a 
long straight smooth and cylindrical tube. 
I].—Dr. Rust, oN THE OCCURRENCE oF RADIOLARIANS IN THE 
CRETACEOUS STRATA. 
BeErirRAGE zuR KENNTNISS DER FOSSILEN JRaDIOLARIEN AUS 
GESTEINEN DER Kretps, von Dr. Rust, in Hannover. Palzon- 
tographica, Bd. 34, 1888, pp. 181—214, Taf. xxii. bis xxix. 
N his first memoir on the Radiolarians from the Jurassic rocks, 
which has been already noticed in the Guou. Mae.,’ Dr. Rust 
called attention to the apparent scarcity of these organisms in 
Cretaceous strata, but a subsequent examination of about two thousand 
microscopic sections of the rocks of this period has shown that they 
are very abundant in some of the lower beds, though very rare in the 
higher beds of the series. Thus, for example, a reddish hornstone of 
Neocomian age from Katzenberg in the Trauchgebirge was so filled 
with Radiolarians that it might properly be considered as a former 
‘«‘ Radiolarian ooze.”’ On the other hand, in the Upper Chalk only two 
species were found, and these were in limited numbers. They were 
very abundant in beds of the age of the Gault at Zilli, near Wasser- 
leben in Saxony, at Oker and Goslar in Hanover, at Braussrote in 
the Basses Alpes, and at Hscragnolles. In these Gault deposits the 
Radiolarians were mostly met with either in the body-chamber of 
Ammonites or in true Coprolites. In these latter they were invariably 
associated with spicules of siliceous sponges as well as fragments of 
other organisms, indicating, the author believes, that the animals 
which produced the coprolites largely fed on sponges. A peculiar 
feature of many of these coprolites is that they are almost entirely 
made up of small oval pellets, which are supposed to be casts or 
moulds of intestinal follicles of the Saurians or fishes through whose 
bodies they passed. 
From the Cretaceous marls of Haldem in Westphalia Dr. Rist 
only records the six species of Radiolarians, which were first dis- 
covered in these beds and described by Prof. v. Zittel, and from the 
flints of the Upper Chalk of this country he obtained but two species, 
Dictyospyris chlamydea, and Dictyomitra Anglica, both of them new 
forms. The author thinks that this paucity of forms in the Upper 
Chalk may indicate their comparative absence in the seas of this 
period, but it is not improbable that the same destructive action 
which has dissolved the siliceous skeletons of most of the Upper 
Chalk sponges, has been still more effectual in destroying the far 
more minute and delicate Radiolarian tests, most of which only range 
between one-twentieth and one-fourth of a millimétre in diameter. 
From the Cretaceous rocks as a whole, 165 species included in 74 
genera were obtained, of which 49 species occur in Jurassic rocks. 
In general characters the Cretaceous Radiolarians more nearly 
1 Dec. III. Vol. IIT. 1886, p. 79. 
