\i; 



of tin- l.ia-sir Ammonite-, receiving scant notice. :nid his f^rnera 

 ii.it BT6H enumerated because "they do n.t agree with n:itur:il 



groo] 



The clarification appears to be Conservative in >pirit. and cal- 

 culated to Bubflerre usefulK tlir needed ^nmpin^ of tin- numer- 

 ous ^pccics which over burthen the original ^eiins. The synonymy 

 is unfortunately remleretl iuext ric:il>le l.y the greiit ditl'erencr 

 ut' (.pinion :is to vnlid diameters entertained by >-ver:il recent 

 M -leiiKit ists. \vlio aj)pear to have cadi dune their liest to increase 

 the pi-evalent confusion, by forming groups which will not 

 coalesce entirely with t hose of their contemporaries or prede- 



IX. 



The following is an epitome of Neumjiyr's arrangement : 



Family I. ARCESTIDJ:. 



Shell smooth or with transverse folds, ribs or strire ; wrinkled 

 layer present in the geologically older forms, consisting mostly 

 of linear, interrupted stria*, seldom (only in Sageceras) granular ; 

 impressions of the mantle attachment, in the triassic forms, with- 

 out or with a but slightly contracted opening always visible on 

 the body-chamber. Anaptychus apparently horny in Arcestes, 

 certainly present in Anmlt/teux. doubtfully so in the other forms. 



Genus ARCESTES, Sucss. (ex partc). 



Shell, as a rule, smooth, sculptureless, seldom with longitudinal 

 Mri;e (Tornati i ; body-chamber long, taking up one to one and 

 a-half whorls. Whorls strongly involute. Aperture usually con- 

 tracted by the border being reflected inwards or by internal ridges. 

 Lobes strongly incised (ladniated ). so that the saddles merely 

 consist of a slender stem with numerous approximated horizon- 

 tal branches, which in turn are divided into smaller branchlcN. 



Many forms have internal nuclei with an open umbilicus, and 

 a terminal whorl with a callous closed umbilieii-. 



i:;n species Trias; one spi-des rermiau. 

 AK< i INATU8, r.ronn. T. lux, figs. i;:;i, T>32. 



fl'iof. Hyatt very properly pn.teM.s against ignoring prior fo 



MI account of a difference of opinion as to the extent of the 

 and the relative importance of the charaet.-r^ -i\en. See Bait. 





