21 
almost complete loss of the left supraorbital sensory canal, 
the anterior extremity of which it is its main function to 
protect.t The existence of the left nasal would cf course 
also be jeopardised by the motion of the intermaxillary 
cartilage over the beak of the mesethmoid, which, whilst 
not affecting the right nasal, would tend to reduce the left. 
It is necessary to assume some co-operative cause such as 
this, since the disappearance of a sensory canal does not 
necessarily involve the reduction of the true lateral line 
bones, or the Plaice would not possess a right !achrymal. 
The nasal of the Plaice is a small semilunar bone attached 
to the right side of the posterior vertical plate of the 
-mesethmoid. It supports the anterior extremity of the 
right and only supraorbital sensory canal, and bounds the 
right nasal sack internally. It is sometimes called the 
turbinal. 
Lachrymal (7?.Lc., L.Lc., figs. 1, 2, 3)—These have 
been modified from the first of the suborbital series or 
chain of lateral line ossicles supporting the infraorbital 
sensory canal, and may hence be called the first sub- 
orbitals. They have also been called the adnasal bones, 
on account of their relations to the nasal sack. In the 
Plaice they differ from the bones of the same name in 
most Teleosts (including the Cod) in being closely 
attached to the cranium. They differ in shape as shown 
in fig. 1, the left being more concentrated than the right 
(the latter best shown in fig. 3). The right lachrymal has 
no connection whatever with the right infraorbital sensory 
canal. Both lachrymals bound their nasal sack externally, 
+ Traquair (loc. cit., p. 284) describes a “‘minute turbinal [nasal] 
ossicle”’ on the left side, supporting the ‘‘remnant of the main [supra- 
orbital] canal of the eyeless side.”” We have found the latter in our sections 
as Traquair describes it (see elsewhere), but not the rudimentary nasal. 
Dr. Traquair’s work, however, is so accurate, that he is doubtless correct in 
this also, 
