1862.] DE KONINCK INDIAN FOSSILS. 11 



This shell must have been composed of spiral coils laterally com- 

 pressed, with a rounded back ; the length of the coils equalled about 

 twice the height. They were feebly embracing, and their transverse 

 section represents tolerably well the half of an ellipse, of which the 

 great axis is equivalent to four times the length of the small one (see 

 PL VII. fig. 1 a). 



The surface is covered with a great number of transverse, irregular 

 ribs, which are sometimes very thin, at others thicker ; they are pro- 

 duced by the successive growth of the shell, and are crossed by 

 small spiral ribs, which are regular and parallel, numbering about 

 sixty on each side. The result of this disposition is, that the surface 

 appears as if enveloped by a network composed of meshes of equal 

 breadth, but of irregular length, depending on the size of the trans- 

 verse ribs which produce them. The shape of the cells is most 

 peculiar : the upper lateral lobe is very deep and tolerably wide, and 

 occupies about one-fifth of the total height of the spiral coil ; it is 

 remarkable from the great number of small denticulations with which 

 it is provided. The lower labial lobe is acutely funnel-shaped, and 

 does not present the smallest trace of denticulations. The three 

 saddles which connect these lobes are rounded, and present nothing 

 peculiar. The only species of Ceratites, hitherto known, which bears 

 any affinity with the one here described is the C. parvus, v. Buch. 

 The transverse ribs of this last are more numerous, and the longi- 

 tudinal ones are wanting. In addition to this, the conformation of 

 the chambers is entirely dissimilar in the two species. 



The entire diameter of this species is 25 centimetres (10 inches) ; 

 the height of the mouth is 6i centimetres, and the width 4 centi- 

 metres. The last spiral coil covers the preceding one to the extent of 

 half a centimetre. This and the next species occur in a brownish- 

 yellow sandstone, while the greater number of the following Cera- 

 tites were found in a rock of a calcareous nature. 



28. Ceratites Mttrchtsoniantts, De Kon. PI. VIII. fig. 1. 



I am acquainted with but half the shell of this large and fine 

 species, upon which I have not even been able to discover any traces 

 of chambers ; but these must have borne some analogy with those 

 of the preceding species. It is probable that the only fragment 

 known represents in itself the last air-chamber, and that it is from 

 this cause the septa are wanting. This specimen bears evidence that 

 the coils of the spire were slightly compressed on their sides, that 

 their dorsal portions were rounded, that they were feebly embracing, 

 and that they produced a large umbilicus. The surface is covered 

 with rather large transverse ribs, which occupy only the sides of the 

 shell, and are in no way prolonged on the back, which, seen in pro- 

 file, forms a very regular curve. The ribs are not of equal width ; 

 they bifurcate or trifurcate without any order, and are eighteen in 

 number on the specimen figured. As those near the mouth are smaller 

 than those which precede them, it is probable that the sides of the 

 first whorls of the spire were strongly ornamented, as may be often 

 remarked among the Ammonites. 



