Clakkk — 1'iik Naples Fauna. 



109 



Family Magnosellaridae, Hyatt. 

 Tobnocebas, Hyatt, 1883. 

 This genus was founded upon the species which is here considered, Gon. 

 miiangularis, Conrad. Some recent writers, principally Zittel,* Fbech f and 

 Holzapfel,J Have expressed the belief that Toeetocebas and Hvait's genus 

 Pabodicebas, founded upon the Gon. disco ideas Hall, are parallel and 

 equivalent terms and have let one be absorbed by the other. Holzapfel has 

 argued for this construction at some length. There is, however, a notable 

 difference in the course of the mature suture in the types of these two 

 subdivisions, but this distinction has been obscured by the confusion of 

 illustration. This fact was distinctly pointed out by Beecheb,§ in a valuable 

 contribution upon the development of Torn, uniangtdare, and upon a review 

 of the original material of these two species, it seems to us necessary that 

 Gon. discoideus be restricted to shells agreeing with that originally figured in 

 the 13th Ann. Rept. N. Y. State Cabinet of Natural History, p. 98, and repro- 

 duced in Palaeontology of New York, volume v, part 2, pi. lxxi, fig. 4, (also 

 figs. 5, 6, 8, 9). This form occurs only, to our knowledge, in the goniatite 

 limestone of the Marcellus shales. 



Whatever generic value, therefore, the term Parodicekas (or Parodo- 

 ceras, which, as Fbech has suggested, is the proper spelling. of the word) is to 

 have, must be derived from the characters of this species. At a more recent 

 date than that above cited, Fbech || has observed that a difference in these 

 shells will be found herein : That Tobnoceeas has a short living chamber and 

 strongly curving growth-lines, while Paeodocebas has a longer living chamber 

 (more than one volution), straighter growth-lines and numerous lateral ridges. 

 The term Pabodocebas has also been lately applied by (tukich^[ to certain 

 Devonian species, on the basis of these differences, supplemented by a 

 departure in the internal course of the suture. Gueich shows that in JParo- 

 doceros saciihts, Sandb. (sp.) the internal saddle is 

 divided into two, thus making an infrasutural lobe 

 which does not exist in typical examples of Tokno- . 



• 1 1 Figure 84. The course of the adult 



oebas. In view of these considerations we have re-ex- 



amined the specimens upon which the genus Pabodocebas, and its type 

 species (Gon. discoideus, Hall) were founded and find the following to be 



• Handb. der Palaeontologie, vol. 2, p. 418. 



Grundziige der Palaeontologie. 

 tZeitschr. derdeutsch. geol. Gesellsch. 1887, p. 442. 



X Das Obere Mitteldevon (Schichten mit Strineocephalus Burtini and Maeneceras terebratum) im Rheinischen Gebirge, 

 p. 80, 1 895. 



{ Amer. Jour. Scl. toI. xl, p. 72, 1890. 

 HZeitschr. deutsch geol. Oeaellach., 1893, p. 331 



1 Verhandl. d. russ. kaia. Mineral. Gesellsch. zu St. Petersb , 2d ser. vol. 32. pp. 339 et sea. 1890. 



