Clarke — Tiik Naples Fauna. 



105 



Probelogekas (?) Naplesense, sp. nov. 



Plat.- VII, Fig. 18. 



Thi s is a representative of the Gephyroceras-Beloceras series which is 

 intermediate, in suture lobation, between Probeloceras and Belogeras. 

 Tentatively it is referred to the former 

 genus, for our observations are re- 

 stricted to a single specimen which in 

 itself does not justify us in now assign- 

 ing to the species the generic import- 

 ance W'llicll LtS Characters SUggeSt. Figaro 78. Probeloceras 1 NapUsenge. The adult suture. 



In external aspect there are no features distinguishing it from Probel. 

 I/uikeri and Bel. iynasj it has the same degree of umbilieation, "the laterally 

 compressed whorls and sharply defined hyponomic keel. The ventral saddles 

 are divided by a faint median lobe, the main lateral saddle is well developed, 

 subacute and inclined tow ard the umbilicus and a harrow, sharp, ventro-lateral 

 saddle is present. The ventro-lateral and lateral lobes are narrow and sub- 

 acute, and the umbilical lobe broad and rounded. 



The species has been found only in the soft shales at Naples, X. Y. 



Genus Sandbergeroceras, Hyatt. 



The shells for w hich this genus was erected have lost the manticoceran 

 saddles and lobes by frequent division, are widely umbilicated, the whorls 

 very broad on the venter and covered with costae. The author of the term 

 has pointed out that the essential generic characteristic is the costation of the 

 whorls, the course of the suture in typical species not being unlike that of 

 Prolecanites. 



The two species (-ml traced within this designation by Hyatt, Gon. tuber- 

 culoso-costatus, Sandb., and Gon. Chemungensis, Hall, differ from each other in 

 the character of their sutures to this extent, that in the earlier and smaller form 

 {Gon. tuberculoso-costcdus) lobes and saddles are equally rounded, while in 

 Gon. Cliemuiuj, en&is, the lobes are all pointed. 



In Belogeras, the multipartite suture has both lobes and saddles acute 

 and a much more discoidal, narrowly umbilicated shell. 



