264 DENNIS, ON FOSSIL LIAS. 



our common bats does not exhibit* them, not to mention other 

 instances In the thick portion of fig. 2, PI. XVI., there are 

 apparent traces of haversian canals which very probably have 

 been ground away in the more transparent portions of the 

 bone, a circumstance of frequent occurrence in grinding ver- 

 tical sections of fossil bone. Figs. 2 and 2 a show admirable 

 lacunas that are in connection with an haversian system, and 

 very nearly compare with that of the wali'us, fig. 8. 



Having made these preliminary observations, we will turn 

 at once to the consideration of the fossil bone, of which fig. 1 

 is a representation, and attempt to determine its true rela- 

 tions. If by the microscope alone it may be shown to be 

 possible to assign it its due position in the scale of animated 

 beings, the achievement will be a brilliant one ; if failure 

 ensues, at least it should be pardonable. Figs. 2 and 3 re- 

 present small vertical sections taken from the lower part, and 

 magnified 100 diameters. Figs. 2 a, 2 0, portions of fig. 2, 

 magnified 400 diameters in fig. 2 b, the lacunae are irregular, 

 and agree, in this respect, with some of the three-toed 

 sloth. The upper end of the bone is composed of fine can- 

 cellated structure : the appearance externally is very fine in 

 the grain like ivory. The bone came from the bone-bed 

 deposit west of Lyme Regis, which rests upon the upper beds 

 of the new red sandstone, and is identical with that deposit 

 which has been called — from, I believe, the circumstance of its 

 first having been observed at Bristol — the Bristol bone-bed. 

 It is principally composed of minute portions of bones and 

 fishes' teeth, and was supposed chiefly to contain the remains 

 of fishes. 



For convenience sake, I shall refer at first to Mr, Quekett's 

 very excellent histological woi"k ; and we have to deal therein 

 with Fishes, Reptiles, and Mammals, for Birds may well be 

 put out of the question. None of the plates on Fishes demand 

 our notice, until we arrive at Plate V., and this requires at- 

 tention. At once we may dismiss the Lepidosiren, as the size 

 and shape of its lacuna?, not to mention other differences, 

 forbid us to compare our fossil with it ; no more can the 

 Megalicthys Hibberti, figs, 1, 2, 3, 4, and 5, be compared with it. 

 We may also dismiss the figures of the Burdie house fossil, 

 for the lacunae of that sauroid fish more nearly agree with 

 those of the pterodactyle. We have now only the supposed 

 Rhizodus to deal with, and a very slight examination of figs. 

 16 and 18, the transverse and vertical sections of the cranium 

 with the plate, will show at once that no agreement exists 



* At least at present I have not detected any. They are hardly 

 apparent in the rib of the rat, and wanting in the scapula, c^c. 



