29 
FOSSILS OF THE PLETA LIMESTONE. 
viz. on the banks of the Pulkovka and Popofka brooks, and on the banks of the 
Tosna. 
It is in these districts that the greater number of the Lower Silurian fossils of 
Russia have been obtained, many of which are figured in the works of Pander and 
Eichwald 1 . In the beds exposed on the sides of the Pulkovka brook, we collected 
the following fossils: Lingula longissima (Pand.), Orthis obtusa (Pand.), 0 . calli- 
gramma (Dalm.), 0 . injlcxa (Pand.), 0 . adscendens (Pand.), 0 . hemipronites (V. Buch), 
Leptcena imbrex (Pand.), Orthoceratites vaginatus (Schloth.), O. duplex ("Wahl.), Illce- 
nus crassicauda (Dalm.), and Asaphus expansus (Dalm.). All the valuable specimens 
(some of them unique) which enrich the cabinets of St. Petersburgli, also come 
from this and other ravines in which the strata are exposed. Besides the two usual 
above-mentioned Trilobites, these strata are found to contain other species already 
known in Sweden or in England, such as Calymene polytoma (Dalm.), C. Fischeri, 
C. sclerops (Dalm.), C. Bowningiae (Murcli.) , Ampyx nasutus (Dalm.), Metopias aries 
(Eichw.), Tr. splmricus (Boeck), and very rarely the Asaphus Buchii and A. Heros 
(Dalm.), or tyrannus 2 . 
Among the brachiopods from these spots we may cite as particularly worthy of 
note the Spirifer lynx (hiforatus, Schloth.), a species around which as a type many 
varieties may be ranged, the Spirifers of the group of £. (squirostris ( Terebratula equi- 
rostris, Schloth.), the Siphonotreta unguiculata, Orthis parva and Crania antiquissima 
1 See Pander, Beit. Geogn. Russland, 1830, St. Petersburgli; and Eichwald’s works, Geogn. Zool. per 
Ingriam marisque Balt. Prov., &c., 1825; Zoologia Specialis, 1829 ; Urwelt des Russlands, H. 1 and 2; 
and Silurische System in Esthland, 1840. Both M. Eichwald and M. Pander have compared the palaeo- 
zoic rocks of Esthonia and St. Petersburgli with those of Sweden, and have shown that the fossils of the 
two countries are essentially the same. 
1 The Asaphus tyrannus (heros, Dalm,), or a form which M. Eichwald thought might be united with it, 
is mentioned by that author as occurring at Odinsholm (Silurian System in Esthland, p. 80). Since then 
it has been found by His Imperial Highness the Duke of Leuchtenberg at Grafskaya Slavenka as well as 
the Asaphus Buchii, an important addition to our knowledge. The quarries of Grafskaya Slavenka and 
Fedorofski, south of Czarskoe-celo, particularly the former, have afforded to the zealous researches of the 
Prince a great variety of other fossils, including three new species of Trilobites, which he has named 
Asaphus centron, A. longicauda, A. liyorrhinus, and Nilcus nanus. Besides some species of Trilobites, Or- 
thoceratites and Testacea, previously named by M. Eichwald and M. Pander, the Duke has further disco- 
vered and named the new species Pileopsis borealis, Terebratula digitalis, with two new species of Crinoidea, 
one of which is termed the Gonocrinitcs giganteus, &c., &c. See “ Beschreibung einiger neuen Thierreste 
von Tzarskoje-celo, von Maximilian Herzog von Leuchtenberg ,” with a copy of which memoir His Imperial 
Highness has honoured us. 
