NO. 1519. MOROSA UR US A GILLS REDESCRIBED—OILMORE. 157 



following comments: "The most important point brought out is that 

 all three skulls exhibit a well-detined tubular opening on top of the 

 skull at the junction of the parietals and. paraoccipitals. This foramen 

 is smoothly lined with l)one and leads directly down into the cerebral 

 cavity." 



Lesser foramina. — The brain cast of Morosojurus grandis., figured by 

 Professor Marsh, shows at its anterior extremity the olfactory lobes. 

 Just anterior to the place these lobes would occupy in the brain case 

 of M. agilis is a large V-shaped opening, through which the olfac- 

 tory nerves must have had exit. (See I, Plate XII.) The opening is 

 bounded above by the frontals and below^ by the orbitosphenoids. 



Twenty millimeters posterior to the olfactory foramen are two deep 

 circular openings, the optic foramina. (See II, Plate XII.) These 

 appear to merge into one another, but if separated at all it is by a very 

 thin septum of bone. In Diplodocus Doctor Holland says they are 

 separated by a "short filament of bone."" 



Posterior and external to the optic foramina, show n best on the right 

 side of the skull, is a subcircular foramen, which probably gave exit 

 to the oculomotor nerve. (See III, Plate XII.) 



Situated at a higher level and posterior to the last-mentioned open- 

 ing is an oval foramen (this is also best shown on the right side of the 

 skull), which, according to analogy of the recent reptilia, is the exit 

 for the trigeminal nerve. (See IV, Plate XII.) 



As mentioned before, where the orbitosphenoids unite with the 

 frontals jiloiig thoir superior lateral margins is <[uite a prominent for- 

 amen, which may have served as an entrance for blood vessels or the 

 exit of nerves. 



Just above the suture between exoccipitals and basioccipital and 

 l)elow the parat)ccipital process in the exoccipitals are three foramina 

 which the writer identifies as follows: The larger and superior one 

 probablv gave exit to the hypoglossal nerve; this opening pas.ses 

 through the exoccipital and enters the posterior margin of the foramen 

 magnum a little in advance of its posterior boundaries. External to 

 the hypoglossal foramen is the foramen for the pneumogastric nerves, 

 while more venti'aily still is the foramen through which the internal 

 carotid artery enters the skull. 



Pro-atlas. — The pi'o-atlas or postoccipital is composed of two sub- 

 triangular lateral pieces; when in position, as found with this speci- 

 men, they are attached to the occiput just above the foramen magnum, 

 and extend backward and outward (see fig. 1, a. and Plates XII and 

 XIII /*. ^4/.), overlapping the neural arches of the atlas, thus affording 

 a protection to the spinal cord at this point. 



These lateral pieces in profile are sut)triangular, flattened, and some- 

 what curved antero-posteriorly. The anterior ends (see fig. 4/^.) are 

 greatly thickened and'somewhat concave transversely, to better fit the 



