158 M. E. Beyrich on the Goniatites. 



traces of striiE. This ammonite is found with the Goniatites 

 of the red Hmestone at Sessacker near Oberscheld. 



11. Ammonites carinatus, n. s. PI. I. fig. 11. a, b, c. 



The dorsal lobe is nearly three times as broad as it is deep, 

 consequently the two sides rise very gradually to the dorsal 

 saddle, the middle elevation of the dorsal lobe is broad, round- 

 ed above, and reaches to about half the height of the lobe. 

 The dorsal saddle is very broad and rounded, and reaches 

 much beyond half the side. The lateral lobe rounded below 

 rises towards the suture, but only to about half the height 

 of the dorsal saddle. The increase in height is 0*45, the in- 

 crease in breadth 0*57. There arc five or six whorls, the 

 inner w horls being almost wholly enveloped, leaving a narrow 

 and deep umbilicus. 



The lobes of this ammonite present a great resemblance to 

 those of the preceding species with which it occurs. The only 

 difference is, that in consequence of the still greater breadth 

 of the dorsal lobe and dorsal saddle the latter extends further 

 over the side, and the ventral wall of the lateral lobe is less 

 raised towards the suture. The last character may arise from 

 the inner whorls being here more strongly involuted, and in 

 consequence a part of the lateral lobe may be compressed by 

 the suture above. The septa of the chambers are hollowed to 

 form a straight and deep ventral lobe at the part where they 

 come in contact with the back of the preceding whorl. This 

 ventral lobe is accompanied by two broad and smooth aux- 

 iliary lobes, which occupy the side of the preceding whorl, in 

 the part which is enveloped. The greatest thickness is near 

 the suture, from whence the side very gradually declines to- 

 wards the back. On the middle of the back, if the shell is 

 preserved, a small elevated ridge is visible, which is unusual 

 in the Goniatites, and can only be produced by the siphuncle, 

 situated immediately beneath the shell. This ridge cannot be 

 seen if the shell is wanting, nor is it found on the unchambered 

 part of the shell ; on that part the back is altogether rounded. 



In the specimen represented the unchambered part is en- 

 tirely wanting. The complete ammonite is many inches in 

 diameter. The shell thick and almost quite smooth. 



