The Morphology of Cosmobia -407 



Trochlearis and is thus positively identified as the superior oblique. 

 The other three pass over and beyond the eyeball, and hence suggest the 

 levator palpebr^, although they are too numerous to correspond with the 

 normal condition of this muscle. The outermost of these three pairs of 

 slips converges in front of the eyeball, and after giving a small slip to the 

 surface of the latter, inserts into a conical sheath of connective tissue, 

 which passes forwards and inserts into the frontal bone. The two inner 

 slips upon either side are closely associated together and run forwards 

 and inwards above the conical sheath just referred to, and in such a 

 manner that the outer ones become dorsal to the other pair. These latter 

 join to form a median tendon, that inserts into a slight projection of the 

 conjoined frontal bone, at a point where a minute canal traverses it. 

 The inner pair, now ventral to the other, passes into a small triangular 

 opening in the connective tissue sheath and becomes inserted into a pair 

 of minute cartilages that for reasons to be considered farther on must 

 be the vestigial tarsal cartilages of the upper eyelid. This latter element 

 then, the innermost of the three extrinsic bands, is without doubt the 

 levator palpebrse, but whether the two other pairs, the one expanding 

 into the sheath, the other inserting into the frontal bone, represent also 

 certain elements of this muscle cannot be definitely decided. It is above 

 all things necessary to determine with certainty the exact meaning of 

 the conical sheath which seems here so important, and for this we must 

 wait for the investigation of another specimen in which the involution 

 of parts has not gone so far, an investigation that must interpret to a 

 certainty the parts that here in their reduced state are unrecognizable. 



Beneath the layer of palpebral muscles lie the intrinsic muscles of the 

 e^-eball, of which the superior obliques have already been noted. [Cf. 

 Plate III, Fig. 6.] The strips that lie upon the outer side are innerved 

 by the Abducens, and are thus definitely shown to be the external recti. 

 Of the rest, which are placed in perfect bilateral symmetry, the superior 

 recti are easily identified by their position. Below the eyeball there are 

 two muscular elements, the one a band, the other a sheet, and these, as 

 well as the superior rectus, are innerved by the Motor oculi. Of these, 

 following the analog}^ of the eyes of the Cyclops type, it is probable that 

 the band is the inferior rectus and the sheet the inferior oblique. This 

 accounts for all the muscles normally associated with a pair of eyes with 

 the exception of the internal recti, and these, which would naturallv 

 come between the two eyeball components, would have no place for 

 development. 



