NATE V. 



Fig. 



1. Ammonites brodioei, J. Sowerby, Min. Couch., vol. iv, p. 71, 1822, pi. cccli. [Brit. Mus.no. 43905.] 



•• Specific Characters. — Largely unibilicate, gibbose, costated ; costae radiating, large and numerous, 

 terminated upon the sides of the whorls by obtuse tubercles, front rounded, plicated ; aperture 

 transversely oblong, curved. 



" Somewhat resembling Ammonite* brocchii, tab. 202, but less gibbose and more strongly marked. 

 The radiating ribs are slightly curved : from each of the tubercles that terminates them proceed about 

 four plaits or lesser ribs, that pass around the front, and meet the tubercles upon the opposite side: 

 i liis part of the inner volutions is concealed. 



"This shell was given me a long while ago, as found on Portland Island, but with some doubt, by 

 my kind and worthy friend, Jas. Brodie, Esq., whose name I wish to perpetuate: from the appearance 

 of the stone I should rather suspect it to have come from the under or Ironshot Oolite." 



[See also PL VII, fig. 3.] 



Fig. 



2. Ammonites parkinsoni, J. Sowerby, Miu. Conch., vol. iv, p. 1, 1821, pi. cccvii. [Brit. Mas. no. 43925. | 



"Specific Characters. — Discoid, with numerous highly elevated radii; whorls numerous, the inner 

 ones exposed; radii slightly arched, bifid near the front which is very narrow and plain. 



" Volutions numerous, with slightly convex sides and narrow edges : the arched radii are bent 

 forward at their outer ends, and nearly meet at an acute angle upon the front, but do not pass over 

 it : the edge of the shell is nearly flat, in the cast it is hollow in consequence of the removal of the 

 siphuncle ; the aperture is oblong, narrowest towards the front. 



" This is the Ammonite so frequently split, polished, and sold at Bath : its outer surface is also 

 often ground and polished, showing ramifying, sinuated, or simply undulated edges to the septa, 

 according to the depth to which it has been worked. Misled by worked specimens that had lost the 

 ilal spare in the middle of the edge, I have erroneously referred this species to the Am. giganteus, 

 at page 55 of vol. i while speaking of such as are found near Keynsham, and those fine specimens 

 given me by Dr. Lettsom, all of which are Hatter than even the variety a of the giganteus, arid have 

 more whorls. The species before us occurs chiefly in Lyas, a stratum not known to contain any 

 silicious deposit; it is consequently never imbedded in Chert or Flint, like the A. giganteus {3. I 

 suspect it also may be found in the lower beds of the Ironshot Oolite, as the specimen now figured is 

 from near Yeovil, and contains vestiges of ferruginous grains. I am indebted to the kind attention 

 of Dr. W. E. Leach for preserving it from the gothic hands of the mason, who is often as destructive 

 <>t the essential characters of fossils, as some dealers still continue to be of the natural forms of recent 

 shells, and who rob them without mercy of venerable coats that had resisted with various success the 

 combined efforts of numerous sea-born enemies, whose ravages even leave marks more worthy of 

 contemplation than the formal beauty betrayed by the file or polishing brush. . . . 



'A section, showing the chambers filled partially with crystallised Carbonate of Lyme, is given at 

 tali. 12 of British Mineralogy. It often extends to 18 inches or more in diameter, and when cut thin 

 and viewed by transmitted light, offers a specious excuse for the unscientific mason." 



