Protanisoceras (Protanisoceras) cantianum  Spath, 1939

Measurements	L	D	H/D	T/D	O/D	H/T
CP-103	53.5	48.6	0.36	0.39	0.36	0.93

Age	Origin
kitchini to subhilli zones Condensel level, Lower Albian	Ardennes France

Description. Reworked specimen in black phosphate with test remains, the end of the shaft and probably the beginning of the terminal hook. The coiling is planar. I did not dare to remove the brittle central gangue. The whorl starting with a septum expands slowly on the shaft then more quickly on the cross, while keeping a slightly depressed circular section. The sutures are invisible. There are 26 ribs with rounded crests and wider intercostal spaces, very attenuated on venter. They are radial, except when approaching the curvature of the cross, where they become temporarily proverse, as on pl. 23, fig. 1a by Casey (1961). The rib index varies from 4 at the beginning to 5 at the end. The ventral region is unfortunately worn but, in raking light, we see that all ribs have two small ventrolateral tubercles. Some ribs are a little stronger than others. No lateral tubercle can be seen.

Remarks. Personal discovery. The specimen comes from the famous condensed level of "coquins" (phosphate nodules) of Machéroménil, in the Ardennes, which provided numerous species of ammonites to d'Orbigny and Raulin. P. (P.) cantianum is distinguished from other Protanisoceras by a relatively larger size, ventrolateral tubercles on almost all ribs, and absent or indistinct lateral tubercles. It is cited in England, in the Paris Basin, and in condensed levels of Escragnolles and Peille in the Alpes Maritimes. In the non-condensed levels of Aube, it is known in the kitchini, floridum and puzosianus zones. The table does not contain specimens of the literature, as we could not find any with measurements.