﻿485 



rapidly towards the dorsum, attaining a fixed position in the fifth 

 septum, if I am right in estimating the first septum drawn by Whit- 

 field as the second.* 



It is much larger in the nepionic stages, contracting as it nears 

 the sixth, and becoming a narrow tube in the seventh septum. 

 Subsequently it again increases by growth as the shell grows larger, 

 so that it has the usual large diameter common in this group. If 

 the trend of the siphuncle towards the apex from the dorsum to 

 the centre is followed out it can be seen that the caecum must have 

 been situated somewhat on the ventral side in the apical chamber. 



The rapidity with which the siphuncle becomes propiodorsan, 

 attaining this position in the metanepionic substage or as the first 

 whorl bends to assume the gyroceran curve, shows affinity appar- 

 ently for Trocholites, but the position in the second septum and 

 the size of the siphuncle and the sutures of later stages are not in 

 favor of this view. The form of the whorl is very similar to that 

 of Schroederoceras Eichwaldi, but from this it is separated by the 

 sutures, which in the ephebic stage on the fourth whorl have slight 

 saddles instead of lobes on the venter and the siphuncle is not so 

 close to the dorsum and is larger. The suture of the earlier stages 

 are straight and are trocholitean in aspect, with well-marked dorsal 

 lobes, as is also the form and ornamentation of the young whorls, 

 which are slightly costated. 



There is a well-marked contact furrow, and I did not find the 

 tendency of the last whorl to become free, as described by Whit- 

 field, the contact furrow being well defined at the termination of 

 the whorls in the original of Fig. 5, PI. xxix, of his work. 



The slower growth and distinct form of the apex, which is more 

 cylindrical and not cap shaped, and the development of the 

 siphuncle, separates it from the young of Schroederoceras Eatoni, 

 and also that of Schroederoceras teres and Trocholitoceras Wakotti. 



Although the position of the siphuncle at an early stage is not 

 yet known in species of Litoceras, this species is obviously dis- 

 tinct because of the narrowness of the whorls, which resemble 

 those of Eaioni in outline. Besides the ventral saddles, the sutures 

 of the fourth volution have well-marked lateral lobes and dorsal 

 lobes in the contact furrow. The whorl remains throughout 

 life in transverse section depressed, elliptical, as in Trocholites, 



*I am not satisfied with this correction. The aspect of the first chamber is move nat- 

 ural in Whitfield's drawing than in mine. 



