. College collection of palaeontology. 96 MOLLUSCA. and Dr. Paul Fischer would raise the family to the rank of ai> order. Excepting the Goniatites, the family is peculiar to, and co-extensive with, the Secondary strata. AmTnonites proper in-^ habited involute shells, having undulating septa, lobed and foliated sutures, a dorsal siphuncle (ventral as regards the animal), and a small nucleus, the whorl being compact from the first. Accord- ing to d'Orbigny, the compressed specimens are males, and the inflated, females. Supposed opercula {Aptychi) are frequently found associated with these she
. College collection of palaeontology. 96 MOLLUSCA. and Dr. Paul Fischer would raise the family to the rank of ai> order. Excepting the Goniatites, the family is peculiar to, and co-extensive with, the Secondary strata. AmTnonites proper in-^ habited involute shells, having undulating septa, lobed and foliated sutures, a dorsal siphuncle (ventral as regards the animal), and a small nucleus, the whorl being compact from the first. Accord- ing to d'Orbigny, the compressed specimens are males, and the inflated, females. Supposed opercula {Aptychi) are frequently found associated with these shells. The shell of the ATnmonites is generally thinner and more delicate than that of the Naxitihvs ; the partitions are consequently moi'e complicated, and the ribs^ are adorned and strengthened with spines, tubercles and bosses. With few exceptions, those having the back keeled, with a furrow on each side, mark the Lias period ; while those with sharp, square or round backs are Oolitic. ATnmonites are rare in tlie Jurassic of America, but abound in Europe, and they have been seen in Oolitic deposits on the Himalayas, 16,200 feet above the sea. The Jurassic ATnmonites were of far higher grade than the living Nautilus. No. 183. G-oniatites Ixion, The Goniatites were the earliest of the family Ammoni- tidae. This specimen closely resembles O. rotatorius of DeKoninck, and is a very characteristic fossil of the Goni- atite Limestone at Rockford, Indiana. No. 183. G-oniatites Oweni, Hall. The most prominent feature separating this species from the preceding is the presence of an umbilicus. Goniatite Limestone, Rockford, Indiana. No. 184. Ceratites nodosus, De Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ward's Natural Science Establishment, inc. Rochester
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