MUSEUM OF COMPARATIVE ZOOLOGY. 89 



Hammatoceras insigne Hyatt. 



A mm. insignis Schlo*. Ziet., Verst. Wiirt., p. 20, pi. 15, fig. 2. 



Aram, insignis D'Orb., Terr. Jurass., Cepli., p. 34 7, pi. 112. 



Amm. insignis Quens'dt, Die Ceph., p. 280, pi. 40, figs. 4, 5. 



Loc. Uhrwciler and Oundcrshofen ; Coll. Dr. Krantz and L. de Koninck. 



Hammatoceras variabile Hyatt. 



Amm. variabilis D'Orb., Terr. Jurass., Cepli., p. 350, pi. 113. 

 Loc. Bantz ; Coll. Dr. Krantz. 



AMALTHEOIDiE. 

 Pleuroceras * Hyatt. 



Abdomen flat, with keel and channels well defined ; keel crenulated ; 

 channels vary from obsolete to deep and well defined. Pilas swelling be- 

 low, tubcrculated; genicular bend prominent. Tubercles lateral, arranged 

 along the line of envelopment. Umbilicus open. 



Ventral lobe narrow and but slightly deeper than lateral lobes; the 

 latter unequally divided. Inferior lateral lobe small, shallow, equally 

 divided. Superior lateral cell only partly exposed on the side, and to- 

 gether with the inferior lateral unequally divided.f 



Sub-Gknus No. 1. 

 Sides of whorls exposed. 

 Pleuroceras hawskerense Hyatt. 



Amm. hawskerensis Y. and B., Phil. Geol. York., p. 164, pi. 13, fig. 8. 

 Loc. Yeovil ; Coll. II. W. Marder. 



Pleuroceras spinatum Hyatt. 



Amm. spinatus Brug., Ency. Meth., t. 1, p. 40, pi. 14. 

 Amm. spinatus D'Orb., Terr. Jurass., I., p. 209, pi. 52. 

 Loc. Whitby, Yeovil, Avallon, Quedlinburg, Coburg, Franconia, Banz, 

 Cundershofen, and Canal du Danube : Coll. Mus. of Stuttgart, Dr. Krantz, 

 L. de Koninck, Bronn, Marder, and Boucault. 



Pleuroceras costatum Hyatt. 



Amm. costa'us Schlot., Pet., p. GG, pi. 12. 

 Naut. cotta'us Rein., Naut. et Argo., p. 87, figs. G8, 69. 

 Amm. costatus Ziet., Verst. Wiirt., p. 5, pi. 4, fig. 7. 

 Amm. costatus Bronn, Leth. Geog., pi. 22, fig. 12. 



* TVKtvpov, a rib. 



t Septa are described from one species only, — Pleuroceras spinatum. 

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