20 



MOLLUSCA. 



Ammonites. 



pi. VIII. fig. 1. but differs from it in the flatness of the keel, 

 and in being provided with two ribs only to each tubercle ; 

 and is distinguished from A. auritus, pi. VII. fig. 9, by the 

 volutions being inserted. 



103. A. BiRCHii Birch's Ammonite, pi. XIV. fig. 7. 



Ammonites Birchii. Sowerby, Min. Conch. III. p. 121, 



pi. 267. Fleming, Brit. An. p. 246 ; De la Beche, Geo. 

 Man. p. 374. 



Discoidal, with from six to eight wholly exposed, gradually 

 increasing volutions ; sides concave, each volution ornamented 

 with about thirty pairs of tliin, obtuse tubercles, each pair 

 united by a slightly elevated rib ; back rounded with obscure 

 sulci, which traverse the sides, on which, however, they are 

 nearly obsolete ; aperture transverse, its length being very 

 little more than its breadth ; greatest diameter seven inches 

 and a half. 



Found at Lyme Regis, Dorsetshire, by Colonel Birch, and 

 named in honour of him : it also occurs at Charmouth and 

 Cragraouth, and in the Lias in the middle and south of Eng- 

 land. 



104. A. GooDiiALLi Goodhall's Ammonite, pi. XIV. 



fig. 10. 



Ammonites GoodhalU. Sowerby, Min. Conch. III. p. 100, 

 pi. 255 ; Fleming, Brit. An. p. 243 ; De la Beche, Geo. 

 Man. p. 296. 



Discoidal, carinated ; with five ribbed, somewhat rapidly 

 increasing volutions, the inner ones one- third inserted ; both 

 edges of the volutions gradually rounded ; sides nearly flat, 

 and provided with large, broad, undulated, irregular, rather 

 flat ribs, obscurely tuberculate at both ends ; between the 

 principal ribs, sometimes shorter ones intervene, these have 

 tubercles at the outer ends only ; keel thin and very promi- 

 nent ; aperture oblong, slightly compressed in tiie centre. 



Found at Blackdown, Devonshire, in the Lower Green- 

 sand, by H. H. Goodiiall, and named in honour of him. 

 Mantell also records it as a fossil of the Lower Greensand of 

 Sussex ; and in the same at Lyme Regis, according to De 

 la Beche. 



105. A. Bennetianus Bennet's Ammonite, pi. XV. 



fig. 1. 



Ammonites Bennetianus. Sowerbj', Min. Conch. VI. p. 77, 

 pi. 539. Fleming, Brit. An. p. 248. De la Beche, Geo. 

 Manuel, p. 295. 



Sub-globose, with from four to six rapidly increasing 

 volutions, the inner ones partly concealed, having a row of nine 

 or ten large conical, blunted tubercles on each side, and a 

 series of twenty very large obtuse tubercles invest each side 

 of the back or ambit ; these are connected by prominent, 

 obtusely rounded ribs, which are stronger and more numerous 

 between the series of tubercles than upon the inner sides of 

 the volutions, and become quite obsolete upon the narrow 

 space over the siphuncle ; aperture transversely oblong. 



In the very young state, the aperture is nearly circular, 

 without any appearance of tubercles; but as it increases in 

 dimensions, the aperture gradually becomes wider, and the 

 tubercles begin to emanate from the ribs, and soon assume a 

 produced aspect, those upon the sides being always the 

 largest and most prominent. 



Found among the Tile Greensand Clay at Cockerton, near 

 Warminster. 



106. A. TETRAMMATUs The Four-Tubercled Ammonite. 



pi. XV. fig. 2. 



Ammonites tetratnmatus, Sowerby, Min. Conch. VI. p. 166, 

 pi. 587, fig. 2. De la Beche, p. 294. 



Discoidal, carinated, with four or five convex volutions 

 crossed by numerous obscure furcated ribs, each furnished 

 with four round, blunt tubercles, the external ones compressed, 

 and two on the shorter branches ; carina sharp and entire. 



This species bears a considerable resemblance to some of 

 the varieties oi Ammonites varians, pi. Vlll. more especially 

 to that of fig. 5, in which there are some of the sets of 

 tubercles in fours, but these are only towards the aperture, 

 all the otliers being in pairs ; the A. titrammatits is, besides, 

 always a larger shell than the A. varians, and has invariably 

 four rows of tubercles. 



107. A. Vernoni. — Vernon's Ammonite, pi. XV. fig. 3. 

 Atnmonites Vernoni, Phillips, Geo. Yorkshire, I. p. 138. 



pi. 5, fig. 19. De la Beche, Geological Manuel, p. 370. 



Discoidal, with three or four rounded volutions, the inner 

 ones nearly half inserted ; the sides furnished with numerous 

 elevated furcated ribs, which emanate from the inner sides of 

 the volutions, and when they reach tlie centre, split into two 

 branches of nearly equal thickness, and passing over the 

 rounded back, meet and join those of the opposite side ; 

 aperture oblong. 



Discovered in the Oxford Clay at Scarborough, by Mr 

 Bean, and is also found in the same kind of strata at Ebber- 

 ston, Lincolnshire. 



108. A. WiLLiAMSONi. — Williamson's Ammonite, pi. XV. 

 fig. 4. 



Ammonites Williamsoni. Phillips, Geology of Yorkshire, 

 L p. 131, pi. 4, fig. 19. De la Beche, Geo. Manuel, p. 370. 



Shell, with five or six thick, slightly raised volutions, the 

 inner ones wholly exposed ; sides crossed by numerous 

 straight, elevated, parallel ribs, which rise from the inner 

 margin of the volutions, and pass continuously over the broad, 

 flat, and thick ambit, and end on the inner margin of the 

 volutions on the opposite side ; aperture oblong, nearly 

 quadrangular. 



Found in the Coralline Oolite at Ayton, Yorkshire, by 

 Mr Williamson, and named in honour of him by Professor 

 Phillips. 



109. A. viTTATUs. — Tiie Filleted Ammonite, pi. XV. fig. 5. 

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



164, pi. 13, fig. 1. De la Beche, Geo. Manuel, p. 372. 



Discoidal, carinated ; with four or five slightly raised 

 volutions, the inner ones a third inserted; the sides crossed 

 by numerous straight, slighth' elevated ribs, which have a 

 slight curvature forward at their outer extremity, and termi- 

 nate on the side of the sharp, thin, and elevated carina, ever^' 

 rib provided with two tubercles, one at each extremity ; those 

 on the inner side but slightly raised, and the outer ones 

 round and well defined. 



Found in Calcareous Nodules in the Lias of Yorkshire, 

 according to Young and Bird, and Professor Phillips. 



110. A. GowERiANus. — Gower's Ammonite, pi. XV. fig. 6. 

 Ammonites Goiuerianus. Sowerby, Min. Conch. VI. p. 94, 



pi. 549, fig. 2. Phillips, Geology of Yorkshire, I. p. 141, 

 pi. 6, fig. 21, a variety. De la Beche, Geo. Manuel, p. 370. 

 Compressed, deeply umbilicate ; with six or seven convex 

 volutions, the inner ones half inserted, deeply sunk below 

 the level of the outer one ; sides crossed by numerous 

 elevated and sharp ribs, which take their rise from the inner 

 edge of the volutions, and extending over half of the sides. 



