36 



MOLLUSCA. 



Nautilus. 



Discoidul, unibilicate ; inner volutions entirely concealed, 

 and rapidly increasinfj ; sides rounded, smooth ; aperture 

 sub-rotuiiil ; siplmiifle placfil closu to the back ; septa dis- 

 tinct ; umbilicus large and deep. 



Professor Phillips says, there are three varieties of this 

 species : A, has a circular umbilicus, with the inner volutions 

 partly concealed ; B, umbilicus somewhat angular, with the 

 volutions more involute ; C, umbilicus open and rounded, 

 and the shell somewhat less involute. The two former are 

 found at Bulland, Queen's County, and the latter are from 

 Kildare, Ireland. 



32. N. BisTRiALis The Doubly Striate Nautilus, PI. 



.\XV. fi-. -2. 



Aaulilus biitrialis. Phillips, Geology of Yorkshire, II. |). 

 232, pi. 17, fig 2. 



Discoidal, unibilicate ; inner volutions entirely concealed ; 

 sides slightly rounded ; umbilicus very large, but not deep, 

 with several spiral strife on its margin. 



Found at Bolland, Queen's County, Ireland. 



33. N. GONioLOBATUs. — The Corner-Lobed Nautilus, pi. 

 XXV. fig. 3. 



\uiUilus goniolohus. Phillips, Geology of Yorkshire, II. 

 p. 232, pi. 17, fig. 23. 



Involute, suhglobose, unibilicate ; inner volutions wholly 

 concealed ; sides smooth, inflated ; ambit rounded ; umbilicus 

 small ; sutures retroflexed in a small dorsal sinus ; first lateral 

 lobe angular ; the second cannot be traced 



Found at Bolland, Queen's County, Ireland. 



34. N. iNGENs. — The Huge Nautilus, pi. XXV. fig. 4. 

 NatitJus ingeiis. Phillips, Geology of Yorkshire, II. p. 232, 



|)l. 18, lig. 4. De la Beche, Geo. Manuel, p. 428. 



Discoidal ; inner volutions slightly concealed, and increasing 

 rapidly ; sides smooth ; ambit round ; aperture orbicular, 

 obscurely angular towards the inner edges ; siphuncle round, 

 placed at about a third the length of the aperture from the 

 ambit ; septa numerous. It is a very large species. 



Found at Coniston, near Gargrave ; and at Clattering- 

 dykes, in the Mountain Limestone. 



It is nearly allied to A', pentagoiius, pi. 22, fig. *21, but may 

 be distinguished from it by the roundeil ambit. 



35. N. LINEATUS — The Lincated Nautilus, pi. XXV. fig. 7. 

 Nautilus lineahis, Sowerby, Min. Conch. I. p. 89, pi. 41. 



Fleming, Brit. An. p. 229. De la Beche, Geo. Manuel, 

 p. 36'J. 



Spheroidal, compressed, umbilicate; inner volutions entirely 

 concealed ; sides slightly flattened, and obscurely striated 

 transversely ; umbilicus small and well defined ; ambit flat, 

 broad, with a sjiiral concave groove in its centre ; aperture 

 somewhat quadrangular, with a deep indentation from the 

 preceding volution ; siphuncle placed near the middle ; septa 

 very numerous and concave, with three slight marginal 

 undulations ; diameter about a third longer than its thickness. 



Found in the Inferior Oolite at Combdown, near Bath. 



36. N. SULCATULUS. — The Sulcated Nautilus, pi. XXV. 

 fig. 8. 



Nautilus sulcatuliis. Phillips, Geology of Yorkshire, II. 

 p. 233, pi. 17, figs. 18 and 25. 



Discoidal ; inner volutions quadrangular, partly exposed ; 

 sides smooth, concave towards the outer edge, and convex 

 towards the marginal slope, which terminates abruptly, with 

 many acute sigmoidal, transverse, and a few spiral strix> ; 

 volutions quadrangular ; ambit concave along its centre, and 



somewhat bevelled to the sides ; aperture oblong, some- 

 what ten-sided ; siphuncle situate near the outer edge. 



Found at Higli-Green-W ood, and Kildare, Bolland, and 

 Coalbrookdale. 



37. N. tLtCASs. — The El' gant Nautilus, pi. XX\'. fig. 10. 



Nautilus degans. Sowerb\, Min. Conch. II. p. 33, pi. 116. 

 Fleming, Brit. An. p. 229- Mantell, Geology of Sussex, 

 p. 112 and 197, pi. 20, fig. 1. jil. 21, figs. 1, 4, 8. De la 

 Beche, Geo. Manuel, p. 293. 



Subglobose, umbilicate; inner volutions one-third con- 

 cealed ; sides with numerous transverse, linear, curved, 

 reflexed sulci, which divide the surface into broad flat ribs, 

 which, alter funning an elegant curve on the ambit, proceed 

 laterally, and are tliiii reflected towards the umbilicus ; aper- 

 ture obtusely sagittate ; the siphuncle large, placed central ; 

 septa concavo-convex, etitiie, undulating in a gentle man- 

 ner, with their convex surface placed in an opposite direction 

 to that of the grooves, and drcussating them ; umbilicus very 

 small. Greatest diameter twilve inches ; its greatest thickness 

 is equal to about twice its width. 



This species is pretty widely dittused, and is met with in 

 the Gray Chalk .Marie of Sti.nehain, llamsey, Ott'hani, Kans- 

 coinbe, Middlehaiii, and Firle, in Sussex. 



In a young condition, the furrows are wide, and separated 

 by sharp transverse ribs, and the whole surface is ornamented 

 with numerous well defined striae. 



3B. N. ANNULAKis. — Tiie Kinged Nautilus, pi. .XXV. 

 fig. 11. 



Nautilus annularis. Phillips, Geology of Yorkshire, I. 

 pi. 12, fig. 18. 



Discoidal, with a large circular aniiulation ; sides gently 

 raised ; aperture very large ; septa remote, and but slightly 

 curved. 



Found in the upper Lias Sliale of Yorkshire. 



39. N. KECALis. — The Hoyal Nautilus, pi. XXV. fig. 12. 

 N^auti/us rfgalis. Sowerby, Min. Conch. IV. p. 77, pi. 355. 



Fleming, Brit. An. p. 230. 



Gibbose, destitute of an umbilicus; inner volutions entirely 

 concealed; sides plain and com ex; ambit flattened; aper- 

 ture somewhat wider than long ; sides expanded, with a 

 considerable indentation by the volution, and a little straight 

 next the back. Largest diameter about nine inches, and its 

 thickness about five. 



This species somewhat resembles N. iiiijurialis, pi. 24, 

 fig. 5, but ditt'ers in its volutions, increasing more rapidly 

 than in that shell, and its solid axis. In the young state, it 

 may also be distinguished by the convex sides of the aperture. 



Found in the London Clay, at a depth of sixty feet. 

 Regent's Canal, Hyde Park, and Island of Sheppey. 



40. N. ExPANSus. — The Expanded Nautilus, pi. XXV. 

 figs. 13 and 14. 



Nautilus crpansus. Sowerby, Min. Conch. V. p. 83, pi. 458. 

 fig. 1. Di' la Beche, Geo. Manuel, p. 293. 



Subglobose, umbilicate ; inner volutions wholly concealed ; 

 sides with fine, sharp, transverse strin?, which following the 

 lines of growth, pass from the umbilicus in an elegant sweep 

 over the -rounded back, and proceed conlinuously to the 

 umbilicus on the opposite side ; umbilicus small, and nearly 

 circular ; aperture transverse, very greatly exposed, laterally, 

 so much so as to make the axis considerably longer than the 

 diameter of the shell ; the septa intersect the striae and in 

 front their edges are nearly straight. 



