90 BLUE CHALK MARL. 



bercle, and proceed with an elegant curve from the inner to the outer 

 margin, where they terminate in angular projections, and form the cre- 

 nulated margin of the keel. The septa are sinuate, and very fohaceous. 

 The siphunculus is placed near the inner margin. The aperture is nearly 

 equal in length to half the diameter of the shell, and is deeply indented 

 by the inner whorls. The remains of this truly splendid ammonite are 

 common at Ringmer and Laughton, the specimens varying from half an 

 inch to two inches in diameter. Small specimens are sometimes found 

 with the carene rounded, and the wreaths nearly destitute of radii, in 

 which state they might easily be mistaken for a distinct species. 



Tab. xxi. fig. 13. A portion of the outer volution covered with the shell. 



Fig. 17. A cast in pyritous marl, exhibiting the sinuous 



septa ; smaU crystals of sulphate of lime are contained in cavities on the 

 opposite side of this specimen, and pseudomorphous iron pyrites is 

 disseminated throughout the mass. 



16. Ammonites auritus. Min. Conch, tab. 134, vol. ii. 



" Compressed, with obscure radiating undulations, tuberculated at their 

 origin ; inner whorls exposed ; back deeply channelled, bordered by large, 

 alternating, compressed tubercles." 



Fragments of this species occur at Ringmer ; but none have been 

 discovered sufficiently perfect for representation. 



17. Ammonites jo/o?iMs. Tab. xxi. fig. 3. 



Involute, depressed, volutions deeply inserted, obscurely marked with 

 curved striee ; carene flat, with crenulated borders ; aperture sagittate ; dis- 

 sepiments sinuate. 



The surface of the volutions is nearly smooth, the striae being in- 

 distinct, and in some specimens imperceptible (as in the figure). The 

 inner wreaths are three-fourths concealed ; the situation of the siphunculus 

 is unknown. 



This species is nearly allied to A. splendens, but differs from it, in 

 being destitute of tubercles on the inner margin of the volutions, and in 

 the absence of the radiated markings, with which the surface of the 

 former species is adorned. 



