144 Hall on the 



Plate II. Fig. 1. An individual preserving the connecting 

 membrane almost entire, showing the sinuous outline. 



Fig. 2. A specimen exhibiting the half of an individual, in 

 which the disk is unequally extended between the rays. The 

 margins are apparently entire between all of these ; and from 

 whatever cause or injury this inequality may be due, it existed in 

 the animal while living. 



Fig. 3. A fragment of slate preserving portions of three indivi- 

 duals. The connecting membrane had been removed by mace- 

 ration before they were imbedded in the stony matter ; but the 

 branches are preserved to the length of more than seven inches. 

 It does not appear that the portions preserved present the entire 

 animal ; on the other hand, it is almost certain from the condi- 

 tion of the specimens, that the branches were originally much 

 longer. It will be observed that the branches do not all show 

 the serrated margin at equal distances from the centre, but this 

 is due to the accidental position assumed by the branches as they 

 were imbedded ; some present the exterior surface for a consider- 

 able distance, and, gradually turning, become flattened laterally. 



Fig. 4. The exterior of the base of a specimen, showing the 

 small node or radicle which proceeds from the centre of the vin- 

 culum or connecting stipe. 



The preceding illustrations are of a single species in different 

 degrees of preservation. The manner of branching, although 

 subject to slight modifications, is still always reliable for the pur- 

 poses of distinguishing the species. 



Locality and Formation. — These specimens were obtained at 

 Point Levy, opposite to Quebec, in a band of bituminous shale, 

 separating beds of grey limestone. These strata belong to the 

 Lower Silurian series, and are of that part of the Hudson River 

 Group which is sometimes designated as Eaton's sparry limestone, 

 being near the summit of the group ; they form also the rocks of 

 Quebec. 



Collectors. — J. Richardson, Sir W. E. Logan, and James Hall. 



Graptolithus abnormis. 



Description. — This species, of which only imperfect specimens 

 have been seen, presents four principal branches diverging from 

 the centre, two from each extremity of the vinculum, and each 

 one of these bifurcating and branching unequally, and at unequal 

 distances from the centre. 



