160 M. E. Beyrich on the Goniatites. 



only example at present known of a Goniatite with divided 

 dorsal lobe from the limestone of the Eifel. It has in common 

 with the preceding species its lateral lobe pointed, in its form 

 it approaches nearer to A. carinatus, but is sufficiently di- 

 stinguished from both. The unchambered part of this ammo- 

 nite must be imagined, as the whole of the fragment preserved 

 is chambered. 



14. Ammordtes calculiformis, n. s. PI. II. fig. 3, a, b, c. 



The dorsal lobe is almost as broad as deep, its sides ascend 

 rapidly to the dorsal saddle. The middle elevation does not 

 reach one fourth the height of the lobe. The dorsal saddle is 

 broad, rounded, and occupies half the side. The lateral lobe 

 is also greatly rounded, and does not reach the third part of 

 the depth of the dorsal lobe. Its ventral side ascends towards 

 the suture nearly to the height of the dorsal saddle. The in- 

 crease in height is 0*5, the increase in breadth 0*57. There 

 are five or six whorls, the inner ones entirely disengaged. 

 This ammonite is found with the Goniatites of the red lime- 

 stone of Sessacker, near Oberscheld. From its form it might 

 be taken for a Clymenia, rather than a Goniatite. In the in- 

 ner whorls the flattened back forms a right or rather a sharp 

 angle with the side, from the greatest thickness being imme- 

 diately near the back, and the side descending to form an in- 

 clined surface somewhat concave from the back to the suture. 

 The back is singularly excavated, so that a wide shallow furrow- 

 runs along it. On the last whorl but one the back is broader 

 than the side. The sides of all the whorls are entirely ex- 

 posed. Neither the sharp ridge formed by the back and side 

 nor the furrow^ on the former appear in the last unchambered 

 whorl. In this part the back is completely rounded, and the 

 greatest thickness found in the middle of the side, rendering 

 the section of the mouth very nearly circular. The shell is 

 thin and very elegantly striated upon the last whorl, the striae 

 forming on the side and on the back a smooth curve directed 

 backward. We must further remark that in this ammonite 

 there is a deep ventral lobe, which sinks into the back of the 

 preceding whorl, unaccompanied by the auxiliary lobes on 

 either side. Among the species already described only the 



