520 STUDIES FOR STUDENTS 
Mojsisovics and Waagen,’ on the Triassic faunas of the Alps, 
Himalayas, the Salt Range of India, and Siberia, there is no 
longer any such excuse. Ancestral types, long predicted by 
larval stages of Jurassic ammonites, may be seen in these 
works, as, for instance, 7vopiceltites, which is exactly like the 
neanic stage of Amaltheus; but the great variety is confusing, 
and correlation difficult, on account of unsatisfactory classifica- 
tion. 
The only solution of the problem is to classify genetically 
the Paleozoic goniatites, and from them work upwards into the 
Permian and Lower Triassic ammonites. These older groups 
have simpler larval stages, are not very greatly accelerated, and 
repeat clearly their ancestral history. When this is done the 
radicles will all be known, and when we know the stock of 
the tree, the branches that came off in the higher Trias, Jura, 
and Cretaceous will offer no difficulties. The most systematic 
attempt to do this is Haug’s paper, ‘‘ Les Ammonites du Permien 
et du Trias;’’* but his classification is based wholly on the char- 
acter of the sutures, and neglects other characters, such as 
sculpture and shape of the whorls. Thus Haug’ places Lutom- 
oceras with the prionidian family Zvachyceratide, disregarding 
its ontogeny, which places it undoubtedly with the 77vopztide. 
But no classification based entirely on one character can be 
truly genetic. Hyatt* in his monographs on the ontogeny of 
ammonites has shown us the way; Branco by his studies of the 
larval stages of ammonoids has accumulated a great mass of 
accurate data that can be used with confidence even by the student 
that rejects his theories as to classification. And Karpinsky, by 
using the methods and principles discovered by these naturalists, 
has worked out the genealogy of one of the chief stocks of the 
earlier ammonites. 
1 For the literature on’ Triassic faunas see JoUR. GEOL., Vol. IV, No. 4, J. P. 
SmirH, “ Classification of Marine Trias.” 
2 Bull. Soc. Géol. France, II Ser., Vol. XXII. 1894, No. 6. 
3Op. cit., p. 408. 
4Bull. Mus. Comp. Zool., Vol. III, No. 5, 1872; and Smithsonian Contrib. to 
Knowledge, “Genesis of the Arietidae,”’ and other papers. 
