The Microscope. 327 



18. Wagner, R. — Beitr. zur Vergleichendeu Physiologie. Bd. 

 ii, 1838. NachtrJige zur Vergl. Physiol, des Blutes, p. 13. First 

 announcement that the red blood -corpuscles of adult and larval 

 lamprey eels are circular and bi-concave. 



19. Weber et Souchard. — De la Disposition en Piles 

 qu' AflPectent les Globules Rouges du Sang. Arch de Phys. Normal 

 et Path. 1880, p. 521-531. Figures and describes rouleaux in 

 the vessels of the mesentery of a living dog. 



20. Welcker, H. — Grosse, Zahl, Volum, etc., der Blutkorper- 

 chen. Zeit. F. Rati. Medicin, 3d Reihe, XX Bd. See note to table 

 of measurements, above. 



Cornell University, Ithaca, N. Y., Aug., 1888. 



NOTES ON THE DIATOMACEOUS FORMATIONS OF VIR- 

 GINIA IN CONNECTION WITH SOME RECENT 

 DISCOVERIES MADE IN THE EXCAVATION 

 OF THE EIGHTH STREET TUNNEL 

 AT RICHMOND. 



C. L. PETICOLAS. 



"^ I HE Richmond beds underlie perhaps one-half the area of the 

 -*- city, and are found at depths varying from a surface exposure 

 on the slopes of the hills to fifty or more feet beneath at their sum- 

 mits. Their actual extent at this point is about two and a half miles 

 from north to south, by one and a half from east to west. At some 

 points— notably on Broad street — the infusorial is overlaid by beds of 

 stiff blue clay containing many casts of Miocene fossil shells, while at 

 other places, and indeed for the most part, it is only capped by a 

 stratum of ochreous earth from two to eight feet thick, containing 

 Miocene fossils and the gravels, sands and clays of the Quarternary 

 — the Pliocene strata not being shown at Richmond at all. 



Dr. Ruffner, late Superintendent of Public Instruction in 

 Virginia, informed me, that on the road between Richmond and 

 Tappahannock, about forty-five miles to the north-east, this deposit 

 crops out in many places, occupying everywhere the same geological 

 horizon. My own observations at Petersburg, twenty- two miles 

 south, and Wickham's, about the same distance north of Richmond, 

 agree with his, so that we may with confidence refer to the whole of 

 this great formation to the latter part of the Miocene Tertiary age. 

 The lower parts of the stratum usually rest conformably upon beds 

 of dark blue sands and clays, under which lie the Jurassic strata; 



