1876.] 389 [Hyatt. 



Variety BanJcsii. 



Amm. coronatus D'Orb., Terr. Jurass., pi. 168 (not 169). 



Amm. BanJcsii Sow., Min. Conch., pi. 200. 



Amm. anceps-ornati Quenst., Die Cepli., pi. 14, fig. 5. 



This variety retains the Pettos-like form in some specimens until a 

 very late period of growth, and in others a close approximation to 

 the next described variety occurs by the elevation of the abdomen 

 in course of growth, and the gradual rounding of the sides and loss 

 of the tubercles. In Sowerby's collection the original specimen 

 exhibits these characteristics only on the last whorl for a limited 

 space, although the specimen attains the large size of 250 mm. in 

 diameter. In the Mus. C. Z. collection one specimen attains the diam- 

 eter of 220 mm., but exhibits old age only in a slight rounding off of 

 the tubercular projections; in this the sutures are plainly visible 

 throughout. In other specimens, also, the sutures are exhibited in 

 similar relations to the metamorphosed tubercles and form, showing 

 that complete absorption of the living chamber does not occur during 

 growth, and that these changes are truly permanent and retrograde. 

 A form intermediate between these broader and more Blagdeni-like 

 forms and those of the Ornathenthon, or Brown Jura, £, occurs in 

 the collection of the Museum of Stuttgart in the Parkin soni-bed. 



The anceps-ornati of Quenstedt is in no sense a true anceps. It is 

 very similar to " anceps" but a close inspection indicates, first, that 

 there are no intermediate forms between the two, and second, that 

 the form in the Museum of Stuttgart, as above quoted, seems to show 

 that it is genetically linked with the Banksii- and Blagdeni-like varie- 

 ties of the earlier coronatum forms. It is found in the upper part of 

 the Athleta-bed, in the Museum of Stuttgart collection, associated 

 with Bel. hastatus. 



Stephanoceras planulum. 



Amm. planula D'Orb., Terr. Jurass., pi. 144. 



This name is quoted by Oppel, as that of a new species, Amm. 

 Wagneri; but Oppel's comparison shows that he supposed D'Orbig- 

 ny's figure to represent a species closely allied to " arbustige- 

 rus" whereas it very accurately shows the characteristics of a well 

 known French form which passes insensibly into " coronatus," and is 

 found associated with the latter at Chatillon sur Saone in the Bath- 

 formation of Oppel. The originals do not exist in D'Orbigny's col- 

 lection, but young specimens show that their relations are probably 

 correctly stated, as above. 



