Proceedings. 355 



feet of Coal Measures intervene between the Burdie House 

 and the Ardwick Limestones, and we have practically the 

 same Spirorbis in both. It is the simplest of all the species, 

 the coil being open, lax, and imperfect. A great peculiarity 

 of this form, noticed by many observers, was its power of 

 burrowing, or making an impression on the surface of any 

 object to which it became attached. It was also solitary in 

 its habit, and is frequently found upon the fronds of 

 fossil ferns. The other variety which occurs in our micro- 

 scopic sections, 6". Ambiguus^ has a nautilus-like section 

 when cut through the centre. Mr. Etheridge says 6". 

 Ambigiius appears in the marine limestones to take the 

 place of the burrowing form 6". Pusillus^ which is so 

 essentially characteristic of the brackish water deposits 

 of the same epoch. In S. Ainbigims the tube is globose, 

 dextral, whorls one to one and a half, but concealed by the 

 last volution. This species is decidedly gregarious, living 

 in small clusters. The form certainly appears in all 

 the lower Levenshulme limestones where the mollusca 

 and fish remains are present, and it is not seen in the upper- 

 most limestones. In estuarine formations, where fresh water 

 alternated with brackish and salt waters at certain periods, 

 the varieties of ^/^V^rto may thus help us to judge whether 

 the bed of limestones is of fresh water or marine origin. 

 Many examples oi S. Ambigitus are to be seen in the 

 microscopic sections submitted to the Society. Another 

 form of Annelid seen in our sections is the Serpulites 

 Carbonariiis tubes of thin shelly material from i^ 

 to 3 lines in width. It is distinguished from the Serpiila 

 by its narrow elongated form. Of the Serpula there are 

 many examples, and they are generally attached to other 

 objects. Venmlia are also very common, tiny tubes of 

 wavy form, covering shells ; such are to be seen on our sea 

 coast at this time. There are also many tubular objects 

 with annulations like tiny encrinital stems. These belong 



