168 [September, 



umbilicus; siphunculus nearly central ; septa profoundly undulating, showing 

 on the back a sharp recurved lip. 



This is the largest of the genus found in our rocks, being ten inches in dia- 

 meter. It resembles quite closely N. D aniens, especially in the undulations 

 of the septa. 



Locality, Alabama. 



3. N. angulatus. Shell with the septa regularly curved ; emarginated ; me- 

 dium space wide, flat, obtusely angular; siphunculus large, situated towards 

 the inner margin of the chamber; aperture very w r ide. 



Readily distinguished from N. Dekayi, which it resembles, by the angles on 

 the back, and flat median space. 



Locality, Mississippi. 



2. Ammonites. 



1. Ammonites magnificus. Shell compressed, broadly oval ; whorls rapidly 

 decreasing in size, crossed by coarse nodose ribs ; nodes at each extremity of 

 the ribs, the outer nodes compressed and arranged on each side of the convex 

 median space; septa not greatly ramified, dorsal lobe deeply bifurcated. 



Bears some resemblance to A. Delawarensis, but is a very distinct species. 



Diameter tw r o feet. 



Locality, Pickens county, Alabama. 



2. A. earinatus. Shell covered with prominent, closely arranged ribs; ribs 

 nodose, a little undulating ; nodes in five revolving lines ; nodes on each side of 

 the median line compressed; median line carinated ; whorls rapidly decreasing 

 in width ; aperture ovate. 



From the preceding species this is distinguished by its more numerous and 

 closely arranged ribs and numerous nodes. 



A cast in calcareous sand, having a portion of the siphunculus beautifully 

 preserved. 



Locality, Columbus, Mississippi. Dr. Spillman. 



3. A. binodosus. Shell undulating with lines of growth; nodes in two re- 

 volving lines, equi-distant from the sides of the whorls, inner line more promi- 

 nent ; median space narrow, flat ; aperture elliptic. 



This very distinct species has a considerable part of the shell remaining com- 

 pletely silicified. 



The narrow, flat median space, the absence of ribs, and two distinct rows of 

 nodes, separate this from its congeners. 



Locality, Vance's Ferry, Alabama. 



4. A. lobata. Shell discoid, smooth, thin towards the circumference ; dorsal 

 lobe finely serrate ; lateral lobes terminating in large bilobed cells. 



This fossil, of which I have only a fragment, resembles A. placenta, but is 

 distinguished from it by the remarkable cells that terminate the lateral lobes. 

 Locality, Noxubie county, Mississippi. Mr. Richardson. 



5. A. ramosissimits. Shell remotely ribbed, slightly nodose; median line com- 

 pressed ; septa profusely foliated, aperture oval. 



The fragments of this fossil in our possession are at once recognised by the 

 very numerous subdivisions of the lateral lobes of the septa, which cover the 

 entire surface. 



Locality, Sumter county, Alabama. 



6. A- angustus. Shell with the whorls compressed crossed by distinct some- 

 what nodose ribs, each terminating in a robust knob, outside of which is a series 

 of compressed tubercles; mpdian space narrow and carinated. 



Locality, Columbus, Mississippi. Dr. Spillman. 



3. TlTRRFLlTES. 



1. T. alternatns. Shell turreted, spire dextral ; whorls angulated, lower side 

 ornamented by two tuberculated carinas, transversely plaited ; plaits double the 

 number of tubercles, alternately terminating in a tubercle. 



