220 PERMIAN FOSSILS. 
In this species the outer chamber or that which has been tenanted by the animal 
is long; as shown by the complete cast of it, represented in Pl. XVII, fig. 14: the 
whorls increase rather slowly in width; and are flatly rounded at the back and 
sides: the siphonal sheath is large, continuous, and excentrically situated,—passing 
through the septa nearest their inner margin (vide Pl. XVII, figs. 14, 15 a, fig. 
16 a): the septa are slightly undulated at the margins: the sides of the aperture are 
a little prolonged beyond the medio-dorsal region, which is sinuated (vide Pl. XVII, 
figs. 13, 14): and the whorls slightly embrace each other. Nautilus concavus, J. de 
C. Sowerby, of the Carboniferous system, appears to be a closely related species.’ 
Nautilus Freieslebeni occurs in Shell-limestone at Humbleton Quarry, Tunstall Hill, 
Silksworth, Dalton-le-Dale; and in the compact beds at Whitley Quarry. Professor 
Phillips possesses a specimen which he collected at Aldfield, Yorkshire. It is found, 
according to Dr. Geinitz, in the under Zechstein of Milbitz, and Répsen near Gera, 
Corbusen near Ronneburg, and Ilmenau in the Thuringerwald. 
NavtiLus BowERBANKIANUS, King. Plate XVII, figs. 17, 18, 19. 
Diagnosis.—Deeply umbilicated. _Worls increasing rather rapidly in size; slightly 
embracing each other; evenly and continuously rounded on the back and _ sides 
between the latero-ventral angles; decussated superficially with incremental strie, 
and numerous fine raised longitudinal lines. Aperture somewhat orbicular: margin 
rounded at the sides, and sinuated medio-dorsally. 
This beautiful species is readily distinguished from the last, in having its dorsal 
and lateral surfaces evenly and continuously rounded, in the whorls increasing more 
rapidly in size, and in the more rounded form of its aperture. From certain 
markings, which appear to be due to the plates, I am led to suspect, that these 
structures have their margin concave at the sides of the whorls, and pointed at the 
medio-dorsal line; as in the carboniferous MVautilus clitellarius,? which the present 
species somewhat resembles in form. 
Nautilus Bowerbankianus is a rare fossil, having but once occurred to me at 
Tunstall Hill in Shell-limestone, and at the north end of Black Hall rocks in a 
brecciated and probably equivalent deposit. 
den Hornern gerundeter Halbmond. Der Sipho liegt in einem Drittheile der Hohe von der Bauchseite an, 
in deren Mitte die Kammerwand eine kleine einspringende Vertiefung bildet. Die diinne Schale zeigt zarte 
Zuwachsstreifen, welche sich auf dem Riicken in einen breiten und tiefen Sinus herabbiegen.’’—Versteiner- 
ungen, p. 6. The diagnosis in the text is slightly altered from the above. 
1 Trans. Geol. Soc. Lond., 2d series, vol. v, pl. xl, fig. 6. 
2 I feel much pleasure in naming this species after Mr. J. S. Bowerbank, to whom I am under deep 
obligations for numerous emendations in the present work, during its progress through the press. 
3 Transactions of the Geological Society of London, 2d series, vol. v, pl. xl, figs. 5, 5 6. 
