164 Rev. J. F. Blake — On Ammonites. 



With regard to Sowerby's Am. plicatilts, we seem as mncli in the- 

 (lark as ever. We cannot be sure that the tj'pe has been found. 

 The specimen figured by Miss Healy is one which " bore no label, "^ 

 and it by no means appears to be the original specimen when we 

 can " compai'e it with Sowerby's original figure " ; though perhaps 

 the presence of " a few crystals of carbonate of lime about it " could 

 prove that it is the type ; nor can we even be certain that it belongs 

 to the same species, though this may be probable. If there is one 

 thing on which Sowerby may be depended, it is to give indications 

 by which his specimens may be recognized. He seldom, if ever, 

 ' restores ' his pictures ; but in tliis case we find a broad band along 

 the periphery which he would have to imagine, he has made the 

 bifurcations originate often towards the inner half of the whorl, he 

 has run them quite across some suture-lines and has omitted all 

 suture-lines except those at the end, even omitting to mark two 

 deep holes which ai*e left by them, and he has added even a pro- 

 jecting keel beneath the siphuncle, though this may be from another 

 specimen. Nevertheless, the description is also at variance with 

 the figure, but agrees better with the description of A. hiplex, as 

 shown by placing the latter in italics beneath it. 



Discoid radiated, sides flat, front round, plain in the centre, 



Discoid costated, sides depressed, front is round, 

 volutions exposed, i"adii numerous, equal, straight, 



volutions exposed, costa numerous, small, nearly straight, 



furcate, aperture square with rounded angles. 



split over the front,aperture oblong, narroioer near the front, whichis round. 

 The radii do not branch till they begin to turn over the front, 

 Costce are divided into two branches a little before then pass over the front. 

 in the centre of which they are nearly obliterated. 



It is seen that the main difference indicated is in the character 

 of the centre of the periphery, but somewhat similar features may 

 be seen in some of those corresponding to tab. 293. I think, 

 however, tliey are speciall}' characteristic of shells of the type of 

 tab. 166 (though they seem to be referred by Miss Healy to 

 wearing only) ; for the ends of the half ribs are obscurely seen in 

 the photograph to be swollen on each side of the median line ; the 

 other diffei'ences are mismatched, as: — 'small' for 'equal,' 'nearly 

 straight' for 'straight,' and 'a little before' for 'not till they begin.' 



We shall never know for certain where Sowerby's figured 

 specimen came from till one like it has been discovered in situ in 

 the same sandy stratum at Dry Sandford or Marcham with the 

 several associates recorded, including ' Am. excavotns,' but Phillips saj's 

 nothing about that locality, and speaks only of Headington. Mean- 

 while the new figure most resembles two specimens in my collection 

 from the summit of the Trigonia-beds of Weymouth (whence, 

 ill fact, Buckland may have brought his unlabelled specimen), in 

 which case it represents the highest zone of the local Corallian. 

 Its nearest foreign equivalent, already recognized in the British 

 Islands, is Am. Achilles of D'Orbigny (Terr. Jurass., pi. 206). which 



