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It is plain that the coiled young represents the nepionic and 

 neanic stages and that the aperture must have differed essentially 

 in these stages and perhaps may have been open or else more like 

 that of Cyclolituites. 



Notling also demonstrates in his paper in the Zei/schrif/ that the 

 earlier stages had compressed whorls, the abdomen broader than 

 the dorsum, and also that the siphuncle was nearer the dorsum in the 

 youngest stage observed, and gradually departed from this towards 

 the centre, becoming dorsocentren in the ephebic or outstretched 

 whorl. In old age it again changes its position and tends towards 

 the dorsal side. Notling has also shown that the siphuncle was 

 ellipochoanoidal, consisting of short funnels and the usual porous 

 sheaths, or that which corresponds to this part in the siphuncles of 

 other forms. The structure of the siphuncle in the younger stages 

 was, however, not described or figured. A list of the species ac- 

 cording to Notling is as follows : L. lituus, De Montfort; L. per- 

 fec/us, Wahlenberg; to this Holm added, L. Tornquisti, Holm, 

 and gave very instructive figures of the two species already known. 

 L. diicors, Holm, has a broad dorsal crest in the lines of growth 

 and aperture and is here referred to Ancistroceras, and L. app/a- 

 natus Remele. 



Ange/inoceras, n. g. 



There are several species usually referred to Lituites which can 

 neither be included in this genus nor in Ancistroceras or Holmiceras. 

 These have open coils in the young, and the usual lituitean out- 

 stretched free whorl in the ephebic and gerontic stages. The only 

 species known to me are those described by Angelin and Lindstrom 

 in their Fragmenta Silurica. The lines of growth, and the annuli, 

 during the neanic stage, have curves similar to those of Cyclolituites 

 in A. /a/us, viz., with deep ventral sinuses, crests at the abdomi- 

 nal angles, deep lateral sinuses near the dorsum and dorsal crests. 

 These curves change in the ephebic whorl, becoming less sinuous, 

 but, beyond the fact that they differ very much from those of 

 Ancistroceras or Lituites, they cannot be defined with accuracy from 

 the figures given. 



The increase by growth is more rapid than in Lituites and less 

 rapid than in Ancistroceras, in A. /a/us and in A. anguinus it is 

 very slow throughout life. The ephebic whorl is extended with the 

 usual lituitean curve and closely resembles in aspect, but not in the 



