908 



proportion to their length, and thereby fill up the interspace between the centrum and the 

 diapophysis. The neural spines remain as yet unossified ; the neural arch is incomplete : 

 the cartilaginous basis of the spine is preserved in some of the lumbar vertebrae. In the 

 second and third sacrals, ossification extends a shorter way into the neurapophysis, leaving 

 the canal more widely open. 



Presented by Prof. Owen, F.R.S. 



5880. The bones of a Foetal skull, separated, and artificially connected with each other. 



They are numbered on coloured labels to correspond with the TABLE or SYNONYMS. 



The elements of the neural arch of the occiput (i, 2, 3) are distinct : the paroccipital is 

 an exogenous prominence of the exoccipital (2). The bodies of the two cranial segments or 

 vertebrae, in advance (5, 9), are anchylosed together and with the neurapophyses (10) of the 

 third segment. The neurapophyses () of the second vertebra are still distinct. The neural 

 spines of each of these three segments are likewise distinct ; that of the occiput (3) being 

 partially bifid, those of the parietal (7) and frontal (n) segments entirely so. The elements 

 of the neural arch of the nasal segment (13, 14, is) are similarly distinct. Of the haemal arch 

 of this segment the spine (22) is bifid, and each moiety has partially coalesced with the 

 haemapophysis (21), which is modified for the lodgment of teeth. The germs of some of 

 these, including the two incisors and the two molars, are displayed on the left side. The 

 diverging appendage of this arch includes three bones, one (24) sen-ing to attach the arch to 

 a succeeding segment (e) ; a second (20) modified to aid in forming the orbit ; the third (27) 

 to aid in completing the lateral walls of the immensely expanded neural canal. The diapo- 

 physis of the parietal segment (a) is autogenous, but has coalesced with the bony capsule of 

 the organ of hearing (ie). The pleurapophysis of the frontal segment (23) is separated from 

 that segment by the intervention of part of the expanded diverging appendage (27) of the 

 maxillary arch : it consists of a slender bar of bone bent almost into a circle : the rest of the 

 haemal arch of this segment is modified to support teeth, and forms what is called ' the lower 

 jaw.' The specific names which the other elements of the cranial segments have received in 

 consequence of their adaptive modifications will be. seen by reference to the Numerals in the 

 TABLE OF SYNONYMS corresponding with those in the text. 



Purchased. 



5881. The separated bones of the Foetal skull. 



They are numbered on coloured labels to correspond with the TABLE OF SYNONYMS. 



Mus. Heaviside. 



5882. A Foetal skull, from which the moiety of the bifid spines of the frontal (n) 

 and nasal (is) vertebrae have been removed to show the relations of their 

 centrums (9 & is) and neurapophyses (10 & u) to their respective haemal arches 



(SO 22 & 2832). 



The individual bones have been numbered on coloured labels according to the TABLE OF 

 SYNONYMS. 



Presented by Prof. Owen, F.R.S. 



