8- BULLETIN OF THE 



Amm. planicosla D'Orb., Terr. Jurass., Ceph., p. 242, pi. Go. 

 Loc. Whitby, Yeovil, Semur, Besancon, Gundersliofen ; Coll. Sir C. 

 Lye!! L. de Koninck, Prof. Bronn, and M. Boucault. 



Microceras crescens Hyatt. 



Loc. Whitby and llautenberg bei Schbppenstadt ; Coll. L. de Koninck, 

 Dr. Krantz, and Prof. Bronn. 



This species is closely allied to Microceras arcigerens ; it differs, how- 

 over, in being mure robust, the young are larger, the radii of the spiral in- 

 crease faster, and the sopta differ in having a very deep ventral, and very 

 shallow, superior lateral and inferior lateral lobes. The minor lateral lobes 

 are also of the simplest kind, the superior and inferior lateral cells being 

 but slightly indented by them. 



Microceras arcigerens Hyatt. 



Amm. arcigerens Phil. Geol. York, p. 1G3, pi. 13, fig. 9. 

 Loc. Whitby, Semur, St. Cyr bei Lyon and Aargau ; Coll. L. de Ko- 

 ninck, Prof. Bronn, and M. Boucault. 



Microceras maculatum Hyatt. 



Amm. capricornus nudus Schlot. Petrefactenkunde. 



Amm. maculatus Young and Bird, Geol. York, pi. 14, fig. 12. 



Amm. maculatus Phil. Geol. York, p. 135, pi. 13, fig. 11. 



Amm. capricornus nudus Ziet., Yerst. Wiirt., p. 6, pi. 4, fig. 8. 



Amm. capricornus nudus Bronn, Leth, Geog., Sh. 4, p. 340, pi. 22, fig. 1. 



Amm. capricornus nudus Quens'dt, Der Jura, p. 9G, pi. 12, fig. 3. 



Loc. Lyme Regis, Whitby, Semur, Pouilly, Besancon, Milhaud Dep. 

 L'Aveyron, Gundershofen, Rautenberg bei Schbppenstadt, and Ce^enberg; 

 Coll. Sir C. Lyell, Damon, L. Agassiz, Dr. Krantz, and M. Boucault. 



Microceras sinuosum Hyatt. 



Loc. Pouilly en Auxois, Venarey pres Semur, Gundershofen, Pveutlingen, 

 and Brunswick ; Coll. M. Boucault, Dr. Krantz, and L. de Koninck. 



This species differs from Planicosla in its development, acquiring the 

 pihe at an earlier age of growth, and from M. arcigerens and .1/. maculatus 

 in the forward bend of the, abdominal pihr, the double row of tubercles 

 ornamenting the lateral pih-e of the adult, and the more complicated char- 

 acter of the septa. 



Abdominal lobe with abrupt sides. Minor lobes long and narrow. Su- 

 perior lateral lobe broad and shallow ; inferior lateral, proportionately very 

 narrow. Superior lateral cell very broad ; inferior lateral, much longer 

 and narrower, and very irregularly and deeply cut by minor lobes, resem- 

 bling in this respect the upper portion of the superior lateral cell. 



