Notices of Memoirs — Prof, Nicholson on Palceo%oic Worms. 309 



beds is due as muck to their unfavourable position, as to tlie percola- 

 tion of water from only cropping at the escarpment of Cross Fell. 

 Zinc ranges from the Little Limestone down to the base of the 

 Great Limestone. Copper from the top of the Scar to the top of 

 the Tynebottom Limestones, especially in the copper hazles. Lastly, 

 the greater the inward dip, the larger the supply of metaL 



iTOTiciES o:f 3yc:E];:]vnoi::RS. 



I. — Contributions to the Study of the Errant Annelides of 

 THE Older PALiEOzoio Rocks. By H. Allbtne Nicholson, 

 M.D., D.Sc, M.A., Ph.D., F.E.S.E., Professor of Natural 

 History in University College, Toronto. [Proceedings of the 

 Eoyal Society, May 8th, 1873.] 



IN this communication the author endeavours to elucidate the 

 abundant and obscure organic remains which are found so 

 commonly in the Paleeozoic rocks, and especially in the Silurian 

 strata of Britain, and which are generally known by the vague and 

 convenient names of "Fucoids," " Annelide-burrows," and "tracks." 

 After expressing his opinion that the first step towards the study of 

 these obscure fossils lies in the provisional grouping and naming of 

 the more marked forms which are already known to exist, the author 

 proceeds to divide the remains under consideration into two great 

 groups. In the first of these groups are those fossils which are truly 

 the burrows of marine worms, as distinguished from mere trails and 

 surface-tracks. Some of these burrows (Scolithus) are more or less 

 nearly vertical in direction as regards the strata in which they are 

 found ; and they are to be looked upon as being true burrows of an. 



habitation. In this section are placed the genera Scolithus, Areni- _,3l- - 



colites, and Histioderma. Other burrows are of a totally l^THeren't ?*-6. ■2.«9 

 nature from the preceding, and may reasonably be compared to the 

 burrows of the recent lobworms. These burrows run more or less 

 horizontally as compared with the laminae of deposition, or they 

 penetrate the strata obliquely. They are not burrows of habitation, 

 but are wandering tunnels excavated by the worm in its search after 

 food. The fossils of this group, therefore, as preserved to us, are 

 not the actual burrows themselves, but the burrows filled up with 

 the sand or mud which the worm has passed through its alimentary 

 canal. The burrows of this kind (including, many forms previously 

 described under the names of Chondrites, Palceophycus, etc.), the 

 author groups together under the name of PlanoJites. 



The second great group of Annelide-remains comprises genuine 

 surface -trails or " tracks," which of necessity never pass below the 

 surface of the bed on which they occur. Some of these remains, 

 such as Crossopodia, are, beyond doubt, due to the operation of 

 marine Annelides ; but it may be a matter of question whether we 

 have in these cases the actually petrified body of the worm, or 

 merely the track produced by the passage of the animal over the 

 surface of the mUd or sand. The author, however, gives reasons for 



