Vol. 70.] DEVELOPMENT OF TRAGOPHYLLOCERAS LOSCOMBT. 355 



some authors. to the group of Phylloceras capitanei. Another 

 Phylloceras, mentioned by Neumayr (1879) from the Psilonotus 



Beds, has a larger umbilicus and less numerous constrictions, and 

 therefore comes very near to the young Mhaeuphyllites Stella. If 

 we further remember that there are constricted and non-constricted 

 Mhacophyllites of the Stella group, and that the constrictions in 

 ' Phylloceras ' itself differ widely, as is shown when comparing, for 

 instance, Ph. sylvestre Herbich (1878) with the above-mentioned 

 Ph. togatum Mojs., it will be seen that neither whorl-shape and 

 involution, nor ornament and constrictions in the adult, will enable 

 us satisfactority to separate these ammonites into Phylloceras on 

 the one hand and Phacophyllites on the other. Evidence of the 

 development alone (especially of the development of the suture-line) 

 will permit us to approximate to a rational classification of these 

 early forms. 



Mhacophyllites might, as Pompeckj (1895, p. 39) suggested, be 

 restricted to the ornamented forms, preferably the transsylvanicus- 

 diopsis group. Meneghiniceras denotes the crenulate development, 

 whereas Dasyceras and Schistophylloceras appear to be special 

 lateral developments. The former is not identical with Euphyllites, 

 as Prinz (1905) seems to think, since it has a rhacophyllitic suture 

 and no constrictions ; the latter may be used for the sulcate forms 

 (Sch. aulonotwm Herbich, and Sch. sulcatum Yadasz) which are 

 restricted to the lowermost Lias. Carinate forms (not necessarily 

 sulcate on casts) which appear at several horizons {uermoesense, 

 pars in Wahner ; eceimias Hauer ; planispira Reynes), but do not 

 give rise to any progeny, cannot be satisfactorily separated as yet. 



As has been stated before, all these forms, on account of their 

 normally diphyllic saddles, appear to be descendants of Discophyl- 

 Jites, and are certainly not in the ancestry of the genus Trago- 

 phylloceras with its monophyllic external saddle. Muphyllites, 

 however, which has a psiloceratid suture-line in addition to con- 

 strictions, appears to be more closely related to the stock which. 

 later, produced Tragophylloceras. 



It is by no means suggested that Euphyllites is in the direct 

 line of ancestry of the genus Tragophylloceras. ISuphyllites has 

 compressed whorls, and begins to develop, not only strong lateral 

 ornament, 1 but incipient crenulation of the periphery, such as is 

 observed solely on body-chambers of Tr. loscombi. But the course' 

 of the radial line, the constrictions and the suture-line indicate 

 close relationship. The suture-line is not unsymmetrical, as in 

 Psiloceras, nor is the suspensive lobe so typically developed as it is 

 in Ps. calliphyllum Wahner. The saddles, on the other hand, 

 are triphyllic, although Wahner says that the external saddle 

 is intermediate between Psiloceras and Phylloceras and, therefore, 

 subdiphyllic. Wahner thinks it curious that in ISuphyllites, as 

 well as in Phylloceras (Phacojjhyllifes), two forms should occur 



1 The apparently big- ribs of the innermost whorls are merely the raised 

 portions of the lateral area between successive constrictions, and not costas. 



