FOUETH, OR COEONICEEAN BRANCH. 171 



The shell of variety A is smooth for three or three and a half volutions ; the 

 tubercles begin to spread entirely across the sides on the first quarter of the 

 fifth whorl, and about this time the genie ulae have become prominent. The chan- 

 nels are not present in any of these specimens, but more or less faintly marked 

 narrow depressed zones may be observed on either side of the keel. This variety 

 leads directly into the next, in which the depressed zones become channels. The 

 genicute differ in aspect from those of variety A, because they abut against the 

 well defined lateral ridges of the channels. 



Variety B has the pike developed at about the same period as in variety A, 

 but the channels appear in the young, and on the second quarter of the fifth 

 volution they are quite distinct. 



There is one specimen of variety A in which the pike are slightly inclined 

 posteriorly, and the geniculas more prominent than in any other specimen. A 

 very slight sinking of the abdomen in this specimen would produce a form of 

 variety C, which is found at Eobin Hood's Bay in England, and which has a 

 keeled, channelled, and flattened abdomen. The single suture which was exposed 

 in this specimen possessed remarkably pointed and serrated superior and inferior 

 lateral saddles, and very broad, rounded, but serrated superior lateral lobes. The 

 auxiliary saddles and lobes were pointed and serrated. There was a very large 

 siphonal saddle, and all of the larger lobes and saddles appeared of about the 

 same depth and length. 



One specimen of this species from Balingen was received in exchange from 

 the Museum of Stuttgardt, under the name of Nodoiianiis. Two specimens in 

 Quenstedt's collection belonged undoubtedly to this species, variety A. One 

 from Lias, a, Pforen, named Amm. falcaries (No. 4428), and one from Goppingen 

 (No. 11182), were in the Arietenkalk. The last was 63 mm. in diameter and 

 a typical form of variety A; the pilse are, however, inclined posteriorly, while in 

 the other they are pointed forwards. In the specimen from Pforen the pilse begin 

 abruptly near the abdominal side unpreceded by tubercles. Other specimens, 

 especially the original of his figure, Plate VII. Fig. 6, also from Pforen, show 

 that Hartmanni and this species have intermediate varieties. 



Several forms are found in the Semur collection under the name of Hettan- 

 gensis, Rey., one of which has smooth young, with fine pilations and an adult 

 whorl having close resemblances to this species and also to Am. miserabile, var. 

 acaiidorsale. 



Third Subseeies. 

 Arnioceras kridioid.es, Hyatt. 



Plate II. Fig. 28. Siimm. PI. XII. Fig. 8. 



Ophioceras kridioides, Hyatt, Bull. Mus. Comp. Zool., I., No. 5, p. 75. 



Amm. kridion, Quenst., Der Jura, pi. vii. fig. 8, Amm. Schwab. Jura, pi. xi. fig. 5, 6 (not fig. 7). 



Amm. Bucklandi carinaries, Quenst., Amm. Schwab. Jura, pi. xi. fig. 8. 



Localities. — Basle, Semur. 



This species approximates in aspect to Cat. raricostatum, and was on this 

 account at first erroneously referred to that species. The shell is, however, 



