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, ]5 a, fig. 

 16(2) : 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 Freiesleheni occurs in Shell-limestone at Humbleton duarry, 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 Ropsen near Gera, 

 Corbusen near Ronneburg, and Ilmenau in the Thuringerwald. 



Nautilus Bowerbankianus,^ King. Plate XVII, figs. 17, 18, 19. 



Diagnosis. — Deeply umbilicated. Wliorls increasing rather rapidly in size ; slightly 

 embracing each other ; evenly and continuously rounded on the back and sides 

 between the latei-o-ventral angles ; decussated superficially with incremental striae, 

 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 hne ; as in the carboniferous Nautilus 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, welclie sich auf dera Riieken in einen breiten und tiefen Sinus berabbiegen." — Versteiner- 

 ungen, p. 6. Tbe diagnosis in tbe text is sligbtly altered from tbe above. 



1 Trans. Geol. Soc. Lond., 2d series, voL v, pi. 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. 



8 Transactions of the Geological Society of London, 2d series, vol. v, pi. xl, figs. 5, 5 b. 



