146 



globose, and others more compressed bj' age ; but tbej 

 generally lose some of the ornaments from their last 

 whorls, and in their infant state are also smooth, or free 

 from tubercles, bearing- some analogy to the higher 

 orders of the animal creation, whose middle ages are 

 generally the most beautiful. No species perhaps un- 

 dergoes a greater change than the one before us, where- 

 fore it is named mutabilis. 



AMxMONlTES subarmatus. 

 TAB. CCCCVIL— >^. 1. 



Spec. Char. Depressed, concave, ribed, in- 

 ner whorls almost wholly exposed ; ribs 

 curved, often united in pairs by smooth 

 spines; aperture transversely oblong, 

 arched. 



Syn. Ammonites subarmatus, Younq- and Sird, 

 GeoL of Yorks* p. -250. t. 1.'), /: .3. 



U TON the last formed whorls of this shell, the spines dis- 

 appear, and the ribs which in the former whorls are gene- 

 rally split before they pass over tbe front, are not so 

 often divided ; the spines continue nearly to the centre, 

 they are hollow, and leave when the shell is removed, a 

 blunt cost, but not a truncated tubercle as in the A- libu- 

 latus ; the whorls have convex sides and encrease rather 

 rapidly ; they are contracted in some parts, in the same 

 manner as the last. 



It is probable that there are several species allied to 

 this, but it will require numerous specimens of each to 

 prove that they are not varieties : the A. perarmatusf of 

 Young and llird, is one thus doubtfully situated, but 

 most probably it is a variety of the subarmatus. 



Found at Whitbv. 



* It is hoped t'nat the latp Mr. Sowerby's veracity and credit, need no 

 defence against the attack^ and false surmises of the arrogant, the Au- 

 tho'-s of the Geoio;Tical Survey of tbe Yorkshire Coast, had not been 

 lavthT noticed, but tha*, 'vhen names are iriven to «hcllo, their Publishers 

 must be quoted, and where any merit exists, it should not be overlooked. 



t We bad not seer t",).e Hrnl. of the Yorksiiire co.im , ^v'.iP^ 4. pcrarma- 

 t-«s, tiib. :'i-j2 was publisiicd. 



