178 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



12. 



umbilicus. The surface around the umbilicus is smooth for about halfway 

 across the whorl, where very numerous, regulai*, rather shallow, somewhat 

 undulated striae, or narrow sulcations, commence, with narrower inter- 

 stices, and continue across the rounded back. The mouth is ovato-iunate ; 

 the septa appear to have been arranged in numerous phylliform lobes, the 

 terminal divisions of which were ovate and large. Belongs to the section 

 Heterophylli, but is rather an abnormal form. 

 Ammonites Leai. Nov. sp. 



a. Side view. 



b. View showing the form of the aperture, and the back of the whorls. 



A. testa compressd, subumbilicatd, involutd, semicostatd, costis numerosis, 

 prope aperturam obsoletis, sulcis undulatis substitutis ; dorso excavato-sulcato, 



sulco Icevi, marginibus carinatis, dentatis. Aperturd subtriangulari. Septis 



Med. semi-diam. 0^ ; m. crass. 4± ; lat. sule. dors. 0| unc. 



A very beautiful little Ammonite, quite perfect, and apparently full- 

 grown. It is compressed at the sides, and flattened and furrowed at the 

 back. The last whorl envelopes the others, and becomes somewhat dilated 

 at the mouth. That half of it nearest the umbilicus is smooth, the re- 

 mainder marked by numerous well-defined undulated sulcations, which be- 

 come obsolete towards the mouth, where they are replaced by deeper and 

 wider sulci, separated by flattened elevations of equal breadth. The angles 

 of the dorsal furrow are rather acute, and are tuberculated by the raised 

 oblique extremities of the costae between the lateral sulcations. The centre 

 of the back is slightly hollowed out, and quite smooth. The mouth is wide 

 and triangular, though truncated at the top. The septa are not visible. 

 Belongs to the section Dentati, and is nearly allied to several gault Am- 

 monites. 



13. Ammonites bogotensis. Nov. sp. 



a. Side view ; the outline of the complete shell restored. 



b. View of the back. 



A. testa compressd (subumbilicata ?) radiato-striatd, subsulcatd, dorso piano 

 subexcavato, sulco dorsali lato, Icevi. 



Lat. frag. 1 7 2 2 . Crass. 0-^ unc. 



