18 



MOLLUSCA. 



Ammonites- 



90. A. CATTNUs. — The Cliain Ammonite, pi. Xllf. fig. 4. 

 Ammoniles Catina, Sowerby, Min. Conch. V. p. 21. pi. 



420. Mantell, Geology of Sussex, p. 198, pi. 22, fig. 10. 

 Buckland, Geology and Mineralogy Considered, II. p. 59, 



pi. 37, fig. 8. 



Depressed, with from six to eight smooth volutions, with 

 flattened sides, the inner ones exposed ; provided with two 

 series of sliort, blunt, moderately sized, conical, round pointed 

 tubercles on each side of the interior and exterior angles of 

 the volutions ; ambit a little convex ; aperture quadrangular ; 

 margins of the septa sharp and deeply siuuated. Largest 

 diameter about thirteen inches. 



Little is known of the perfect condition of this fossil, as 

 little else has hitherto been found of it but casts of the 

 chambers ; these have usually suffered so niucli by the 

 destroying hand of time, that they are but slightly attached, 

 and appear like the concatenations of a chain. From the 

 small portions of the shell which have been seen, it appears to 

 be quite smooth, divested of ribs or undulations, excepting 

 in its young condition. 



Found embedded in sand, in INIarsham Field, near Abing- 

 don, Berkshire. 



91. A. Parkensoni Parkinson's Ammonite, pi. XIII. 



fig. 5. 



Atnmonites Parkinsoni, Sowerby, Min. Conch. IV. p. 1, 

 pi. 307. De la Beche, Geo. Manuel, p. 375. Fleming, Brit. 

 An. p. 244. 



Discoidal, with from seven to nine slightly convex 

 volutions, the inner ones exposed ; crossed by numerous, 

 considerably elevated and arcuated ribs, which are bent for- 

 ward at their exterior ends ; they are furcated near the ambit, 

 which is narrow and plain, upon w'lich they nearly meet ; 

 aperture oblong, narrowed towards the back. Greatest 

 diameter eighteen inclies. 



Found in the Lias at Yeovil, and Holienstein, Saxony, and 

 in the inferior Oolite, Bayeux. 



92. A. Solaris. — The Sun Ammonite, pi. XIII. fig. 6. 

 Ammonites Solaris, Vh^AW'ps, Geology of Yorkshire, I. p. 



135, pi. 4. fig. 29. De la Beche, Geo. Manuel, p. 370- 



Discoidal, carinated, with four nearly flat volutions, the 

 inner ones exposed ; provided with numerous elevated smooth 

 ribs, reaching entirely across the volutions, and slightly bent 

 forward at their exterior ends, where they are terminated 

 by the acutelj' triangular keel ; aperture spatuliform, acute 

 next the ambit. 



Found in the Calcareous Grit at Scarborough, by Mr Wil- 

 liamson. 



93. A. MUTAEij.is. — The Mutable Ammonite, pi. XIII. 

 figs. 7 and 9. 



Ammonites ?nutabilis, Sowerby, Min. Conch. IV. p. 145, 

 figs. 1 and 2. Fleming, Brit. An. p. 246. 



Shell compressed, with from four to five smooth volutions, 

 the inner ones two-thirds exposed, exhibiting tuberculated, 

 wide set ribs ; ambit rounded ; aperture ovato-sagittate. 

 Largest diameter ten inches; thickness of external volutions 

 an inch and a half. 



Fig. 9 represents the shell in its young state, when there 

 is a narrow flattened zone in the centre of the ambit, from 

 whence emanate numerous close-set, somewhat curved ribs, 

 which extend to about the centre of the volutions, where they 

 meet a series of compressed, oblong- ovate tubercles, which 

 reach to the inner margin of the volutions ; the whole interior 



sides of the volutions are smooth. It is only in the very 

 immature state that the tubercles are formed, as they are no 

 longer met with in specimens of two inches diameter; but 

 the external ribs are visible in specimens of six inches 

 diameter, after which they imperceptibly disappear ; and 

 the ambit becomes more rounded, the sides quite smooth, 

 and are somewhat obliquely compressed towards the back, 

 which produces the obtuse sagittate form of the aperture. 

 The external surface is nacred ; and at remote, but unequal 

 intervals, there are slight contractions in the volutions. 



Discovered in the Clunch Clay near Horncastle, by George 

 Weir, Esq. 



94. A. ocuLATUs. — The Ej'ed Ammonite, pi. XIII. fig. 8. 

 Ammonites oculatus, Phillips, Geology of Yorkshire, I. 



p. 138, pi. 5, fig. 16. 



Shell compressed, and slightly depressed ; umbilicate ; 

 interior volutions hidden ; numerous depressed undulating 

 ribs emanate from the margin of the umbilicus, and extend 

 to near the ambit, where they meet a series of very remote, 

 nearly circular, depressed tubercles, between which and the 

 back is smooth ; a series of close-set oblong tubercles invest 

 both sides of the ambit, which is smooth. 



Found in the Oxford Clay at Scarborough. 



95. A. ATHLETA. — The Champion Ammonite, pi. XIII. 

 fig. 8. 



Ammonites athkta. Phillips, Geology of Yorkshire, I. p. 

 141, pi. 6, fig. 19. 



Shell strong, with six volutions, the inner ones almost 

 wholly exposed ; sides crossed by numerous, strong, elevated 

 ribs, with an oblong produced tubercle at each end, those on 

 the outer margin considerably larger than the others ; each 

 of these divide into three narrow exscrted smooth ribs, on 

 the flattened and square ambit, uniting with the tubercles on 

 the opposite side ; the interior volutions gradually diminish 

 in thickness as they approach the centre, the whole side 

 forming a widely reversed cone ; aperture nearly quad- 

 rangular. 



Found in the Kelloways Rock at Hackness, and in the 

 Oxford Claj', Y'orkshire. 



96. A. TUBERCULATUS. — The Tuberculated Ammonite, pi. 

 XIV. fig. 1. 



Ammonites tuberculatus. Sowerby, Min. Conch. IV. p. 4, 

 pi. 310, fig. 1, 2, 3; Mantell, Geology of Sussex, p. 92; 

 Fleming, Brit. An. p. 246 ; De la Beche, Geo. Manuel, 

 p. 294. 



Compressed umbilicate, with five convex volutions, the 

 inner ones two-thirds exposed ; ambit flat ; transversely ribbed, 

 the costae oblong, arising in threes from lai'ge circular tubercles, 

 uniting in pairs towards the back, and forming large com- 

 pressed tubercles on each side of the ambit, which is broad, 

 with a deep narrow sulcus or groove in its centre ; aperture 

 suborbicular ; septa very foliaceous. 



In immature shells, the sides of the volutions are very 

 convex, with a transverse apertui'e ; the tubercles are situate 

 near the centre of the volutions. Length of the aperture 

 about two-fifths of the diameter of the outer volution, and its 

 width varying according to age. 



Found in a stratum of Marie, under the Chalk at Folkstone, 

 and in the Blue Chalk Marl at Ringmer, Sussex ; also in the 

 the same kind of strata at Cambridge, and other parts of 

 England. 



This is a strongly marked species, and has somewhat the 



