The Morphology of Cosmobia 399 



The relations of the eyeball and its associated parts, as revealed by 

 the further removal of the bony roof of the orbit, are shown in Plate II, 

 Figs. 1 and 2. The muscles that arise from the Y-shaped portion of 

 the orbito-sphenoid, as well as the most superficial of these attached to 

 the spine, are shown with cut ends; the remainder are shown in their 

 origin in Fig. 1, and with cut ends in Fig. 2. In the dorsal view 

 there may be first made out the superior oblique, detached from its 

 origin, and the external rectus, arising as the deepest of the three that 

 are attached to the median spine. These two muscles are positively 

 identified from their innervation, and are of great assistance in locating 

 and determining the rest. The remaining detached muscles, of which 

 one is heavy and muscular, the other thin and tendinous, undoubtedly 

 represent the elements of the levator palpebrje. They do not, however, 

 insert directly into the eyeball rudiment, but into a firm membrane (con- 

 junctiva ?) that covers the front of the eyeball, a condition that appears to 

 be more or less usual in such monsters. The two other muscles seen 

 from this aspect take their origin from the median spine, and evidently 

 represent, beginning with the more superficial, the rectus superior and 

 the rectr actor bulbi. The first of these is in nearly its normal relation- 

 ship to both the superior oblique and the external rectus, and the latter, 

 forming with its fellow a broad sheet that covers the eyeball and forms 

 a partial sheath about the median optic nerve, indicates its identity by 

 these characters. 



Upon the ventral aspect, aside from the muscles already identified, 

 there occur two more, fitted into a triangular space that is formed by 

 the two external recti. These are more or less clearly difi^erentiated into 

 two bundles, a more distal one, the fibers of which arise mainly from 

 without, and a nuore proximal one that extends from one side of the eye- 

 ball to the other. These are probably the inferior oblique and the 

 inferior rectus respectively, the elements of the two sides being united 

 into single median elements. The first of these has preserved an origin 

 for each lateral component, and an insertion for a part of it, while 

 the other shows the insertions of the two components, but no origins. 



Adopting the above scheme for the identification of the eyeball muscles, 

 there is but one left unaccounted for, the internal rectus, and this is 

 the very one that would naturally fail to develop owing to the complete 

 suppression of the region to which it belongs. It is also to be noted 

 that the positions and the points of insertion of certain of the muscles, 

 especially such as the external rectus and the superior oblique, which 



