34 



MOLLUSCA 

 De la Beche, Geo 



Nautilus. 



29, fig. 1. Fleming, Brit. An. p. 231. 

 Manuel, p. 429- 



Almost globose, very largely unibilicate ; umbilicus the 

 siiape of a reversed cone, occupying nearly half tiie diameter 

 of the shell, and producing an excavated appearance in the 

 sides; sides smooth, straight, slightly convergent towards 

 that part where the volution enters the aperture ; aperture 

 subquadrangular, considerably produced at the sides by 

 the convex extremity of the umbilicus, arcuated in front; 

 siphuncle nearly central, or rather a little towards the ambit. 



Found in the Inferior Oolite, Dorsetshire. 



15. N. suLCATus. — The Furrowed Nautilus, pi. XXIII. 

 fig- 7. 



Nautilus sitlcalus. Sowerby, Mm. Conch. VI. p. 137, pi- 

 571, fig. 1, 2. De la Beche, Geo. Manuel, p. 429. 



Discoidal ; with four almost wholly exposed volutions ; 

 sides ventricose, with two large spiral furrows, and two or 

 three shallow, broad, smaller ones on each side, upon the 

 most elevated part of the gibbose side ; one of the furrows 

 being concealed in the inner volutions, and with a sharp 

 carinated elevation between the two larger furrows ; ambit 

 concave, aiid bounded by sharp margins ; aperture one-half 

 longer than it is wide, and with its sides indented ; siphuncle 

 situate immediately opposite the inner indentation ; septa 

 numerous, with straight margins. 



Found in the Mountain Limestone at Castleton. 



IG. N. poLYGONALis. — The Many-cornered Nautilus, 

 pi. XXIII. fig. 8. 



Nautilus pohjgonalis. Sowerby, Min. Conch. VI. |). 56, 

 pi. 530. 



Spheroidal umbilicate ; inner volutions entirely concealed ; 

 sides compressed, smooth ; umbilicus very small ; aperture 

 large, arcuated, occupying about half the diameter of the 

 disk, its reflected extremities nearly concealing the umbilicus; 

 siphuncle situate near the outer edge of the septum, and 

 composed of many straight tubes, each protruding a little 

 beyond the septum which it penetrates, to join the preceding 

 tube ; septa distant, considerably concave, with only a slight 

 curvature at their edges ; thickness equal to about two-thirds 

 its diameter. 



Found in the Inferior Oolite, Dorsetshire. 



The whole series of septa have a disjointed aspect. 



17. N. EiANGULATUs. — The Two-angled Nautilus, pi. 



XXIII. fig. 9. 



Nautilus hianijulatus. Sowerbj', Min. Conch. V. p. 84, 

 pi. 45S, fig. 2. De la Beche, Geo. Manuel, p. 428. 



Discoidal subglobose, umbilicate; itmer volutions half 

 exposed ; ambit rounded ; umbilicus very large and deep, in 

 the form of a reversed cone, with its margins acutely 

 carinated ; ajierture transversely elliptical, and obtuse at its 

 extremities, its width being equal to about _^tA0-thirds the 

 diameter of the disk. 



In the joung condition, the extremities of the aperture are 

 angular. 



Found in the Mountain Limestone near Bristol. 



18. N. iiEXAOONUs. — The Six-angled Nautilus, pi. XXIII. 

 fig. 10. 



Nautilus hexaffonus. Sowerby, Min. |Conch. VI. p. 55, 

 pi. 529, fig. 2. 



Somewhat cylindrical, and short; umbilicate ; inner volu- 

 tions entirely concealed ; sides depressed, with a conical 

 angle near the centre ; ambit broad, straight ; umbilicus 



small ; apertm-e sagittate, and truncated on the outer 

 extremity ; siphuncle situate near the inner edge of the 

 septum ; septa tmmerous, and but slightly curved. 



Found in the Calcareous Grit at Shotover Hill, and also at 

 Abingdon. 



19. N. GLOBATUS. — The Globular Nautilus, jil. XXIII. 

 fig. 11, pi. 25, fig. 5, 9. 



uXautilus globulus. Sowerby, Min. Conch. V. p. 129, pi. 

 481. De la Beche, Geo. Manuel, p. 428. Phillips, Geology 

 of Yorkshire, II. p. 248, pi. 17, fig. 20, 28. 



Subglobose umbilicate ; inner volutions few, rapidly in- 

 creasing, and almost wholly concealed ; sides smooth ; 

 ambit flattened ; umbilicus rather small, deep, and provided 

 with a subcarinated margin ; aperture large, very wide, 

 arcuated, and furnished with a deep and wide siims on the 

 back, which divides it into two equal lobes ; thickness and 

 diameter nearlj' equal ; septa numerous ; there is a small sinus 

 formed in the iimer end of the aperture by the intrusion of 

 the preceding volution ; greatest diameter, six inches. 



Found in the Black Bock at Cork. 



20. N. WooDWARDii. — Woodward's Nautilus, pi. XXIII. 

 fig. 12. 



Nautilus Woodwardii. Sowerby, Min. Conch. VI. p. 138, 

 pi. 571, fig. 3. Ammonites Woodtvardii, Martin, Petrifac- 

 tions of Derbyshire, pi. 35, fig. 4, 5. De la Beche, Geo. 

 Manuel, p. 429. 



Discoidal, with four or five wholly exposed, rapidly 

 increasing volutions ; sides of the volutions angular ; the 

 whole surface provided with many concentric series of 

 granulated lines ; ambit rounded, and provided with a 

 linear sulcus in its centre ; aperture obovate, with angulatcd 

 sides. 



Found at Minster, Derbyshire. 



21. N. CENTHALis. — The Central Siphuncled Nautilus, pi. 

 XXIV. fig. 1. 



N'aufih/s cciitialis. Sowerby, Min. Conch. I. p. 11, pi. 1. 

 fig. 1. Fleming, Brit. An. p. 229. 



Involute umbilicate ; inner volutions wholly concealed ; 

 aperture transversely elongate, and bluntly lunate; siphuncle 

 placed quite central ; umbilicus large, but not deep, placed 

 behind the projecting sides of the aperture ; sides smooth ; 

 septa entire, gently bending, concave, but not recurved at 

 their extremities. 



Firrt discovered in Clay, from a well one hundred and 

 seventy-five feet deep, in Richmond Park. 



22. N. cosTALis. — The Ribbed Nautilus, pi. XXIV. fig. 2. 

 Nautilus costalis, Phillips, Geology of Yorkshire, II. p. 



233, 1)1. 22, tig. 30. 



Spheroidal, umbilicate; inner volutions wholly concealed; 

 sides covered with transverse flutings, or ribs ; ridges rising 

 from obscure undulations on the margin of the deep umbili- 

 cus, and terminating in acute projections on the ambit, which 

 are ver^' conspicuous when viewed in profile, with slight 

 contractions at intervals, which are parallel to the ridges, 

 and also with pretty strong elevated stria.-, which lie in the 

 same direction as the ridges ; aperture lunate. 



This species attains a very large size, sometimes measuring 

 fourteen inches. 



Found at Kildare and Queen's County, Ireland. 



23. N. ZiczAc. The Zigzag Nautilus. PI. XXIV. fig. 3. 

 Nautilus Ziczac. Sowerby, Min. Conch. I. p. 12, pi. 1. 



Lowest figures. Fleming, Brit. An. p. 231 ; Buckland, 



