12 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [NOV. 5, 



The fragment described possesses a diameter of 18 centimetres ; 

 the height of the last whorl is 6| centimetres, and its thickness 5 

 centimetres. 



29. Ceratites Haiteriantts, De Kon. PI. III. fig. 5. 



This species, of which I have unfortunately met with but a single 

 fragment among Dr. Fleming's fossils, has much resemblance to the 

 Goniatites Haidingeri, v. Hauer, which may very possibly be like- 

 wise a Ceratites, since in the latter the chambers are extremely 

 numerous, and composed of a great number of very narrow lobes and 

 saddles ; those that occur towards the middle of the spiral coil are a 

 little wider than the others ; they are five in number. Unfortu- 

 nately the specimen is so much defaced that it is impossible for me to 

 describe exactly the shape of the parts of its whorls, which have each 

 eight divisions at least. The back is keeled and tolerably sharp. 

 The thickness of the shell must have been about 2| centimetres. 

 The mouth, seen in front, must have had a subtriangular shape, as is 

 shown in fig. 5 a. 



30. Ceratites planulattjs, De Kon. PL V. fig. 1. 



This fine species, of which I have had the advantage of being able 

 to study one complete and adult example, is distinguished from all 

 those that follow by the angular shape of its dorsal portion. However, 

 this shape does not exist in the young specimens, and is only pro- 

 duced at a certain age of the animal (which is the case also with 

 some Nautili and Ammonites), as is demonstrated by figs. 1 c and 1 d. 



The surface is almost smooth and shining, and is ornamented 

 with fine, radiating striae and undulations produced by the successive 

 growth of the shell. The umbilicus, in the shape of a very widened 

 funnel, allows the several coils of the spire of the shell, five or six in 

 number, to be easily perceived ; they mutually overlap each other at 

 about three-fourths of their height. The number of the chambers is 

 from 30 to 32 for each coil of the spire ; the last chamber is very 

 large, and occupies one-half of the shell. The lobes are shallow and 

 finely crenulated ; the lower lateral lobe is connected with the umbi- 

 licus by means of a sinuous curve entirely free from denticulations ; 

 the dorsal lobe is divided in two by a small elevation, very angular 

 at the summit, and serving for the passage of the siphuncle. The 

 saddles are rounded, and of a moderate elevation. The largest dia- 

 meter of this species is 8| centimetres, that of the umbilicus 18 

 millimetres ; the height of the mouth is 4 centimetres, its thickness 

 19 millimetres, and the width of the back at the extremity of the 

 mouth 4 millimetres. The shape of this species bears some resem- 

 blance to the C. semipartitus, Montf., but differs essentially from it 

 in the shape and number of its lobes. 



31. Ceratites Lyelliantts, De Kon. PI. VI. fig. 1. 



This species is one of the largest among those which have been 

 discovered by Dr. Fleming ; its surface is entirely smooth, its back 

 is rounded, and the umbilicus large. The number of its chambers 



