60 FIELD CoLUuMBIAN MusEUM—GEOLOoGY, VOL. II. 
sphenoid. It would seem that there could be no further question as 
to the character of these vacuities—simply fortuitous openings— 
separated by a remarkably persistent, well-ossified parasphenoid, 
invariably found in all plesiosaurs, but never in their nearest allies, 
the turtles and nothosaurs. In most of the-plesiosaurs in which the 
palate is known, the openings are situated more nearly upon the 
plane of the palate, and, though somewhat variable in shape, are 
always of moderate or considerable size. In this species, however, 
they are at the bottom of a well-marked, rather deep fossa, with well 
defined lateral walls and a sloping posterior roof. 
These foramina in the plesiosaur skull were first thought to be 
the nares by Owen, who, however, confounded the anterior part of 
the pterygoids with the palatines. Huxley, who was also not clear 
about the palatines, suggested that the real internal nares were smaller 
openings situated more anteriorly. Sollas (1. c.) discussed the matter 
more at length and reached the conclusion that the real internal nares 
were situated far in front, between the premaxilla and vomer, with 
the palatines probably entering into the posterior border. Andrews 
has accepted this location of the nares, and has figured and described 
the openings in three genera of the plesiosaurs, always bounded by 
vomer, palatine and maxilla. In Dolichorhynchops osborni, however, 
as seen from the figure and descriptions, these openings can only be 
situated, between the vomers and palatines and at some distance 
from the maxilla. In my description I accepted these orifices as the 
true nares, though greatly astonished at their minute size, and 
although they correspond with similar foramina between the vomers, 
in the mosasaurs. 
If we are to seek for the nares in their present specimen else- 
where than in the openings I have described it must be far forward, 
perhaps in precisely the position assigned to them by Sollas. In all 
the known forms, with this interpretation, they would be in front of 
the external nostrils, in the present species far in front. What 
possible combination of circumstances would have caused the recession 
of the external nostrils to a place so close to the orbits without 
affecting the position of the internal openings? I certainly suspect 
that in this species at least the openings between the pterygoids are 
the real internal nares. As to the character of the separating element 
I am forced to the conclusion that Andrews has reached, that it is 
the parasphenoid. If the element in front called the vomers are 
really those bones, and there could seem to be no doubt that they are, 
there is nothing else left, save possibly the turbinated’ bones.. 
The slender bone in precisely similar position in the ichthyosaurs 
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a 
