72 



that terminates them proceed about four plaits or lesser 

 ribs, that pass around the front, and meet the tubercles 

 upon the opposite side : this 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, Js. 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 Iron- 

 shot Oolite. 



AMMONITES perarmatus. 



TAB. CCCLII. 



Spec. Char. Depressed, armed with two con- 

 centric rows of large pointed tubercles ; vo- 

 lutions exposed, few ; front rounded ; aper- 

 ture nearly orbicular. 



J. HE tubercles are joined transversely by obtuse ridges 

 into 18 or 20 pairs upon each whorl ; the remaining por- 

 tion of the shell is even : it is rather remarkable that the 

 tubercles are as sharp nearly in the cast of the inside as 

 the outside of the shell : there are about four whorls : 

 the aperture is in length about one-third of the diameter 

 of the shell, and is rather longer than wide. 



A very conspicuous Ammonite ; found in the Pisolite 

 at Malton, and given me by Mr. Alexander Crawford, 

 of Scarborough. Besides other characters which distin- 

 guish it from A. Birchii, tab. 267, the acute cast of the 

 spines is a conspicuous one ; the size of these spines will 

 distinguish it from a somewhat similar xlnimonite not yet 

 ligured, found near Oxford, 



