OF THE EARLIER GANOIDS. 32.^ 



mechanism of teeth and plates, together with the spinal car 

 vity and the nostrils. This fifth specimen also exhibits the 

 base of the head ; but the teeth and plates are removed and 

 we look upon the mass of compressed cartilage, traversed by- 

 osseous fibre, on which these rested, and see anterior and pos- 

 terior portions of the cavity which accommodated the brain. 

 The form of the spinal cavity is well shown in this fossil In 

 the sixth specimen, the upper part of the cranial buckler is 

 removed, and we see yet farther into the head. This narrow 

 oblong chamber, fenced by thin slightly-curved partitions, is 

 the brain pan. On each side there were deep cavities for 

 the eyes, represented, however, in the fossil by but blank 

 masses of stone. And higher up, on each side of the spinal 

 passage, there occur somewhat similar but smaller masses, 

 which occupy what seem to have been once the auricular 

 chambers. This seventh specimen shows portions of the eye 

 orbits, — the place of which, until this season, I had failed in 

 ascertaining. With these, this eighth specimen seems to 

 show, though imperfectly, those projecting processes of the 

 occiput to which the apophyses of the spine must have been 

 attached ; but the projection is slightly mutilated. These 

 ninth and tenth specimens show the inner side of the cranial 

 buckler ; and this eleventh specimen its outer side, with the 

 operculum attached. This curious and instructive suite it 

 has taken years to collect ; but the story which it tells of 

 extinct peculiarities, and an old-fashioned strangeness of 

 structure, — linked, however, by broad analogies to the fami- 

 liar and the recent, — I deem more than worth the trouble 

 which the piecemeal disinterment of it has cost. 



I had the pleasure, in the August of 1850, of introducing 

 Professor Owen and Sir Philip Egerton to my collection. In 

 a recent volume, — " Foot-prints of the Creator," — I had men- 

 tioned that in all the cranial bucklers of the Old Red Sand- 

 stone with which I was acguainted there occurred a little 



