528 
DR. A. GUNTHER’S DESCRIPTION OF CERATODUS. 
chord; its attenuation, therefore, appears to be due to the gradual loss of the outer 
cell-bearing strata. 
The neurapophysis of each segment is perfectly distinct from the preceding and fol- 
lowing ; but all are most intimately bound together by intermediate fibrous ligaments, 
in which frequently true hyaline cartilage is deposited. Each neurapophysis (see also 
the sections, Plate XXXVIII. figs. 3-9) consists of a basal cartilaginous portion forming 
an arch over the myelon, and of a superadded second portion, which is separated from 
the former by a distinct line of demarcation, and the two branches of which are more 
styliform, cartilaginous at the ends and in the centre, but with an osseous sheath, and 
coalesced at the top, forming a gable over the Ligamentum longitudinale superius , which 
is enveloped in a layer of fat (Plate XXX. fig. 2, l). To the top of this gable is joined 
a single long cylindrical neural spine, again with the central cartilaginous centre enclosed 
in an osseous sheath, and with an upper swollen cartilaginous extremity. This is the 
arrangement of the first ten segments ; but from the eleventh the cartilaginous swelling 
at the top begins to lengthen into a distinct interneural spine of the same structure as 
the neural. Further on, from the fifteenth segment, another interneural is developed 
in the same manner ; so that in this part of the vertebral column we have the following 
•series of neural pieces : — 
a. Cartilaginous arch of neurapophysis (c) for the formation of the medullary canal ( d ). 
b. Semiossified gable portion of neurapophysis ( e ) over the Ligamentum longitudi 
nale ( e '). 
c. Neural spine (f). 
d. Lower interneural (g). 
e. Upper interneural ( li ), to which the dermo-neurals ( i ) are attached. 
Whilst the increase of the number of neural pieces is the consequence of a lengthening 
of the distal part of the segment, it commences to decrease from the base. We observe 
that all at once, from the thirty-third segment, the neural spine coalesces with the gable 
portion of the neurapophysis; further behind, this portion is gradually shortened and 
finally disappears entirely, so that only the two interneurals remain. Towards the end 
of the tail the neural elements are reduced to a low and narrow cartilaginous lamella 
(neurapophysis) and a single short interneural spine ; and this latter piece disappears in 
the last two inches of the vertebral column. 
In the first three segments the neur- and haemapophyses of each set are confluent, but 
without forming complete rings round the notochord, as the haemapophyses of a segment 
do not coalesce below (see Plate XXXVIII. fig. 3). 
The haemapophyses (Plate XXX. fig. 2, and Plate XXXVIII. figs. 3-9) are, in form, 
size, and structure, very similar to the neurapophyses : those belonging to the same 
segment coalesce below the notochord into a narrow transverse band, at least in the 
anterior portion of the trunk (from the fourth to the twentieth segment). Those of the 
first twenty-seven segments bear well-developed ribs, about 2 inches long, bent outwards 
and downwards in the fore part and middle of the trunk, and backwards and downwards 
