A.MMONITES. 31 



15. Ammonites euomphalus, Sharpe. Plate XIII, fig. 4. 



A. testa inflatd, costatd, tuberculatd : anfractibus latis, dorso depressis, later ibus 

 angulatis, spinosis : costis incequalibus ; majoribus alternantibus latero bi-tuberculatis, ad 

 dorsum bifidis •• dorso depresso, transversim costato, demum iuberculato : umbilico magna, 

 pro/undo : aperturd transversd, angulatd .- septorum marginibus lobis 4 trifidis simpliciusculis . 



Shell gibbous, with a broad flattened back and angular whorls, crossed by numerous 

 unequal tuberculated ribs, which bifurcate at the back ; the ribs are about twenty in 

 number on the side of the whorl, alternately larger and smaller ; the larger ribs bearing a 

 small tubercle near the umbilicus, and a strong spine at the edge of the back ; the number 

 of ribs on the back is about double that on the sides of the whorl, two springing from 

 each spine, curving forwards and meeting again at the opposite spine ; about every fourth 

 dorsal rib is larger than the others, and bears two shght tubercles : umbilicus broad and 

 funnel-shaped, leaving three fourths of the inner whorls visible : aperture transverse and 

 angular : septa with four very simple, trifid, lateral lobes, and the lateral saddle very small. 



Diameter, three fourths of an inch ; width of aperture, half an inch ; height of the 

 last whorl, one third of an inch. 



From the base of the Lower Chalk, at Man of "War Cove, on the coast of Dorsetshire, 

 in the collection of E. H. Bunbury, Esq. 



Only one imperfect specimen of this pretty Ammonite has been seen ; in many 

 characters it is closely related to A. Martinii, D'Orb., having, like that species, the lateral 

 saddle much smaller than the first auxiUary saddle, but it has a flatter back than 

 A. Martinii, and somewhat different ribbing. 



16. Ammonites laticlavius, Sharpe. Plate XIV, fig. 1. 



A. testa discoided : anfractibus paucis, planatis, costatis, tuberculatis ; costis 35 radian- 

 tibus, '^-tuberculatis, dorso interruptis •• umbilico parvo .- dorso, marginibus bi-tuberculatis, 

 medio planiusculo : aperturd rliomboidali. 



Shell with three or four whorls, flattened on the sides ; ornamented on each side with 

 thirty-five equal, straight ribs, each bearing four tubercles, not continued across the back ; 

 in the young shell the ribs are either single, or unite in pairs at the umbihcar tubercle, 

 but after reaching a diameter of three inches, each rib is quite distinct : tubercles in eight, 

 nearly equidistant rows, three on the flat side of the whorl, and one on each side of the 

 back : umbihcus small and well defined, leaving four fifths of the inner whorls visible : 

 back smooth and hollow between the tubercles : aperture rhomboidal. 



Diameter, 6^ inches ; height of last whorl, 3 inches ; width of aperture, 2^ inches. 



A very rare shell in the Grey Chalk of the Isle of Wight. 



This species belongs to the large group of Ammonites with squared whorls and straight 



