Clarke — The Naples Fauna. 



1l>5 



with it a part or all of the siphonal collar which is frequently recumbent on 

 the conch or in contact therewith except at its distal extremity. Our delicate 

 replacements place this fact beyond question. On the sides of the shell the 

 suture makes a gentle backward curve and rises again but not so far on the 

 antisiphonal surface. 



Ornamentation. It may be observed by examination of our figures of 

 young shells, that the surface is crossed by fine, concentric, oblique lines closely 

 crowded together. These liues are rarely seen in the adult shell unless under 

 the most favorable preservation. With advance of age and growth, such lines 

 are combined to form, or are replaced by, obscure broad and low oblique ribs 

 which, like the others, slope backward to the dorsum. These are especially 

 noticeable on the body-chamber but are, nevertheless, often so obscure as t< i 

 be seen only in oblique light. These features, as well as the contour and 

 septatiou of the shell, are precisely those ascribed to B. gracilis by Sand- 

 b-erger. but we observe here in addition, with favorable preservation, a 

 secondary ornament in final growth stages ; fine, vertical, subequal lines, not 

 seen below the body-chamber. 



Early Growth Stage*. The Protoconeh. This is a bubble-shaped body, 

 frequently somewhat unsymmetrical or directed to one side, very broadly 

 sessile upon the end of the shell tube, from which it is separated by a con- 

 striction varying somewhat in depth. We have here presented a number of 

 figures of this primitive shell which indicate a possibility of variation in 

 prominence and size of this body. To a very large degree such differences are 

 due to various modes of preservation. Thus figure 5 represents an internal 

 pyrite cast which shows the asymmetry of the protoconeh and the deep con- 

 striction where it is attached to the conch. Figure 4 is a pyritized shell 

 broken and showing the internal cast. These two specimens show some dif- 

 ference in size of the protoconeh : the apparent difference in the contour of the 

 conch is due to difference in point of view. Figures 1-3, 6 are barite replace- 

 ments of the shell itself which show some difference in the distinctness of 

 the protoconeh : and figure 7 is an internal barite cast which may possibly 

 belong to the other species, B. acicnlam. Several of these specimens show 

 in their continuation the septal features characteristic of this genus. 



Fir*t septum. Not infrequently the delicate protoconeh is broken and 

 such specimens have afforded means of determining the fact that the opening 

 of the sipho in the first septum is distinctly lateral. None of the specimens 

 studied have shown trace of the siphonal caecum. 



