IJS VERTEBRATE PALEONTOLOGY. ,389 



;iik1 most of the published descriptions were made to conform to that 

 view, any attempt now to reverse Fhe application of the terms dorsal and 

 ventral — that is, to call the siphonal side the ventral, and the opposite the 

 dorsal — would necessarily result in confusion. Consequently, to avoid this 

 difficulty, and at the same time not to continue to perpetuate an error by 

 adhering to the old nomenclature, Pictet and some others proposed to apply 

 to the peripheral or outer side, in involute and curved forms, the term 

 siphonal, and to the inner side the term umbilical or antisiphonal. 



To the distinguished geologist and palaeontologist von Bitch, belongs 

 the credit of having first called especial attention to the sutures, or more or 

 less flexed and ramose edges of the septa of these types, as seen in internal 

 casts from which the outer part of the shell had been removed, as a means of 

 distinguishing species and larger groups. These flexures of the edges of the 

 septa that project backward, he called lobes; and the intervening spaces 

 directed forward, or toward the aperture, he termed saddles. Regarding the 

 outer side of the curve of the shell in the Ammonitidee as the dorm/, and the 

 inner or umbilical as the ventral, as has until recently been the prevalent 

 view, he called the backward flexure of the septa situated over the siphon, 

 on the outer side, the dorsal lobe, and the forward projection on each side ot 

 this he termed the dorsal saddle. The next lobe on the inner side of the 

 latter (counting inward toward the umbilicus) he termed the superior lettered 

 lobe; and the second forward projection the lateral saddle. The second 

 lateral lobe he termed the inferior lateral lobe; while the third forward 

 flexure he designated the ventral saddle, and the succeeding lobes and 

 sinuses, between the last and the umbilicus, were by him called the auxiliary 

 lobes and saddles, which he numbered consecutively from without inward to 

 the- umbilical margin. The backward flexure within that part of each volu- 

 tion in contact with, or lapping upon, the next inner turn, and only exposed 

 when the volutions are broken apart, he designated the ventral lobe, which, 

 in species with deeply embracing volutions, is very large. 



This nomenclature of the parts of these shells has been very generally 

 adopted by contemporaneous and subsequent authors, not only for the Ammo- 

 nitidee, but for the straight Baculites, and other genera of complexly septate 

 shells of various forms, until some twenty years back, when a few modifica- 

 tions were proposed. About that time, Pictet proposed to call the lobe on 

 the outer side of the curve, in the involute types, the siphonal or media)) exter- 

 na/ lube, ami the opposite or inner one, the median internal or dorsal lobe. 



