MANtJAL OF THE MOlLUSCA. 



[Family Gokiatidje. Barrande.] 



SJiell involute or straight ; septa concave in their median 

 section ; sutures usually with angular lobes ; septal tubes coni- 

 cal, more or less prolonged, but always directed backwards. 

 Siphuncle cylindrical, of small diameter, always marginal ; 

 siphonal investment not persistent ; convexo-ventral margin of 

 the aperture sloped, lines of growth and ornamentation of the 

 shell with a corresponding sinuosity. 



The genera enumerated in this family are Goniatites, Clymenia, 

 and Bactrites. Dr. Woodward includes the Goniatites and the 

 Bactrites (pp. 196, 197) with ih.Q Ammonitidm ; and the Cly- 

 menia with the Nautilidse (p. 190). 



Family III. — Ammonitid^. 



Shell various ; septa convex in their median section ; sutures 

 always lobed, ramified, or denticulated ; septal tube cylindrical 

 and always directed forwards. Siphuncle cylindroid of small 

 diameter, always marginal ; siphonal investment more or less 

 solid and persistent. Convexo-ventral ? margin of the aperture 

 more or less prolonged, which determines a similar convexity 

 in the lines of growth and ornamentation of the test ; there are 

 rare specific exceptions. 



Division I. — Sutttkes lobed oe denticulated at the base. 



1. Ehabdoceras (see p. 196). 



2. Baculina, D'Orbigny, 1850. 



Example, B. Eouyana, D'Orb. Neocomian, France. 



Shell like Baculites, but its lobes and saddles are not foliated, 

 there being between these forms a similar distinction to that 

 between Ceratites and Ammonites. 



B. acuarius, Schlotheim, is from the Oxfordian strata of 

 Gammelshausen in Wurtemberg. 



3. Cochloceras, Hauer, 1860. 



Etymology, cochlos, a snail-shell, and ceras. 

 Type, C. Fischeri, Hauer, Fig. 8. 



SJiell resembling that of Turrilites, with the sutural lobes 

 simple, as in Bhaldoceras and Clydonites. 

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