542 A. H. Foord — On the Genus Pilocems. 



were preserved, though in a very imperfect condition. These speci- 

 mens have been very kindly entrusted to me for description by Mr. 

 H. H. Howell, Director of the Geological Survey of Scotland. 



They consist of a large number of the detached siphuncles of 

 Piloceras, belonging most probably to more than one species. Many 

 of them exhibit more or less distinct traces of the attachment of the 

 septa in the form of encircling ridges, which give them a ringed 

 appearance. 



Fig. 1. 



Fig. 1. — Filacer as invaginatum?, Salter; .S, /S, remains of septa ; (Si, siphuncle, a 

 little restored in the lower part, with ridges marking the attachment of the septa. 

 (One-half natural size). 



One of them shows the siphuncle in its natural position (Fig. 1). 

 This is probably the Piloceras invaginatum of Salter. The septa 

 must have been extremely thin and fragile, as in most cases they 

 have been broken away from the siphuncle, which is usually found 

 completely detached from them. 



In the specimen I have figured the septa appear as delicate lines 

 upon the weathered surface of the rock. They are from 1^ to 3^ 

 lines distant from each other, measuring them from the narrower to 

 the broader end of the siphuncle. The latter is apparently marginal, 

 as in P. explanator, Whitf. The exact rate of tapering of the shell 

 cannot be ascertained, owing to the absence of the shell-wall on one 

 side of the specimen, but it may be assumed to have been high. 



Another example, showing obscure traces of the septa in contact 

 with the siphuncle, is most probably the small species referred to 

 by Salter in his paper above mentioned, but it is too imperfect to 

 characterize. 



Many of the detached siphuncles in Mr. Peach's collection differ 

 from each other in their rate of tapering, and distance of septa 

 (estimated by the distance of their encircling ridges) ; but I do not 

 feel justified in creating another species out of such imperfect 

 material. The smallest siphuncle in the collection measures 8 lines 



