76 
WHITE LIMESTONE OF CARGOPOL AND ARCHANGEL. 
peasants to form the roads, which in consequence are there excellent. AtBraneva, 
the first station beyond Cargopol, the Spirifer Mosquensis occurs ; and at Volo- 
sofskaya a section exposes hard limestone, subordinate to red and green marls. 
These are covered by white and yellowish sandy limestones, full of fossils, in 
which the Avicula lunulata = Germ ilia lunulnta (Phill.), and the Natica Maria: (nob.), 
prevailed. 
At this locality, where the road makes a bend to the east and south, or towards 
the overlying deposits, we first met with Fusulinse, fossils which we shall hereafter 
show, are abundant in the upper calcareous strata only. The limestone, often the 
white variety, occupying a low ridge between Archangelskaya and Korishevo, is 
even seen to crop out and form ledges for some distance, a rare phenomenon in 
this district, and it reappears at intervals as far as Denislofskaya, beyond which it 
is obscured by the drift of clay, sand and boulders. Wherever the calcareous 
rock comes near the surface, the vegetation is rich in papilionaceous plants, and 
the larch ( Pinus Larix) occurs amid the common northern firs, with which and 
the birch-tree this region is so much covered. At Archangelskaya we collected 
Spirifer glaber (Sow.), S. Lamurckii (Fisch.), S. incrussatus ( Terebratula , Eichw.), 
0. arachnoides (Phill. var.), Productus scabriculus and antiquatus, Cardium elonga- 
tum, Sow. ( Pleurorhynchus , Phill.), Natica Marias (nob.), with Calamopora incrus- 
tans (Phill.) and Cidarites Deucalionis (Eichw.). At Denislofskaya the prevalent 
fossils were Productus antiquatus, Terebratula pugnus (Sow.), and Euomphalus pen- 
tangulatus (Sow.). Beneath the hills, of 150 to 200 feet in altitude, the summits 
of which are occupied by drifted materials, the limestone again appears in a low 
ledge along the edges of the river Dwina. Between Suskaya and Rakolskaya, on 
the road to Archangel, the left bank of this magnificent river (which even here, at 
100 miles above its mouth, is broader than the Thames at Greenwich,) exhibits 
cliffs of limestone, which in summer, when the stream is low, appear at heights of 
thirty and forty feet above the water, and are covered towards the interior of the 
country by mounds and terraces of detritus. 
This white-coloured limestone of the Dwina is rich in organic remains, and con- 
tains many of the species already mentioned in other localities, particularly the 
Spirifer Mosquensis, Leptccna Hardrensis, and two species of Cidaris, one of which 
is the Cidarites Deucalionis. The other fossils are Spirifer rotundatus (Sow.), 
S. rhomboideus (Phill.), Productus punctatus, P. antiquatus, Euomphalus calyx 
(Phill.), Ortliis arachnoides (Phill. var.), with a fish’s tooth. Beds similar to 
