242 SAGECERAS, AMALTHEUS. 



liu- body-chamber. Impression* of the mantle attachment punc- 

 tate or st riate. Wrinkled layer consisting of broken up stria\ 

 Tlfe sut urul lint- of the septa is disi inguished by the presence of 

 external adventitious lobes. Three groups of loles may accord- 

 ingly be dist inguished : 1. The adventitious lobes. -2. The three 

 principal lobes. ;-}. The auxiliary lobes. The adventitious and 

 auxiliary lohe-> always present a similar structure, whilst the 

 principal lobes frequently present a peculiar form. 



Pinacoceras clearly possesses amongst the Goniatites an an- 

 cestor in Gon. miiUilnlxitti*, IJeyr. 



Twelve species from the Triassic. 

 P. METTEBNICHII, Haner. T. lo:j. tio. ;,(;4. 



Genus SAGECERAS, Mojs. 



Is close to Pinacoceras in the form of the shell ami length ot 

 the bo(l\ -chamber, ami differs from it in the structure of the 

 wrinkled layer, the form of the lobes and the direction of the 

 lines of irrowth in the concave portion. The wrinkled layer is 

 coarsely li'ranular. as in Nautili'*, and does not consist of loiiu 

 stria- and threads, as in the remaining Arcesti(he. The saddles 

 are slender, narrow, tongue-like, entire, the lobes syminet rically 

 divided, simply or doubly, by simple conical teeth. Three 

 iiToups of lobc>. a- in Pinacoceras. The lines of growth do not 

 trend backwards, as in /V/wrorr/v/.s-, but forwards. 



Sageceras is already fully developed in the Permian forma- 

 tions, though in these older forms the>iphoiial process charac- 

 teristic of the ammonite staire is wanting. 



Seven examples from Permian and Triassic. 

 SACKCERAS HAIDINGERI, Haner. T. 110. figs. (551, ift'2. 



<;.n..s AMALTHEUS, Monti 1 . 



>iplion:l side of the shell sharpened or carinate ; ribs when 

 present, absent at this part or broken up into tubercles or folds; 

 the iieoh Really older forms with spiral stria 1 on the external 

 layer of the shell, which corresponds to the wrinkled layer of 

 the Areestid;e. Hody-chamber short, one-half to two-thirds of a 

 whorl long; margin of aperture simply emarginnte, with long, 

 external processes, ending in spoon-shaped extremities, some- 



