AiiT. 14. MARYLAND FOSSIL PORPOISE KELLOGG. 19 



fossil skull the external pterygoid comes in contact with the 

 squamosal and the maxilla; these two bones combined limit its 

 ventral expansion. Posteriorly, the external pterygoid sends a 

 process forward and upward to meet the frontal. 



Certain foramina are present in the skull of Platanista which are 

 apparently absent in this fossil skull. No information regarding 

 these foramina can be secured from the right side of the cranium 

 for it has been completely destroyed, and the imperfect preservation 

 of the left side may possibly explain the failure to identify these 

 foramina there. Between the external pterygoid and the frontal 

 there is a small opening which may represent the sphenorbital 

 fissure. 



The lachrymal is missing completely on the left side of the skull, 

 but fragments of this bone are present on the right side. A small 

 fragment of the lachrymal is wedged in between the maxilla and 

 the right supraorbital process of the frontal ; a horizontal, flattened, 

 proximal piece must have filled in the space between the anterior 

 margin of the frontal and the ventral plate of the maxilla. On the 

 left maxilla and internal to the maxillary notch three oblique 

 grooves are plainty visible. These grooves represent the sutures for 

 the jugal which in turn was ankylosed to the lachrymal, as will be 

 shown below. These three features show that the lachrymal when 

 complete must have maintained approximately the same relations 

 with the surrounding bones as exist in the skull of Lipotes. 



In the skull of Liyotes^ the lachrymal is an elongate bone which 

 commences internally behind the opening for the infraorbital canal, 

 and occupies the interval between the frontal and the ventral plate 

 of the maxilla. It extends outward and its distal extremity is 

 closely appressed to the anterior face of the supraorbital process 

 of the frontal. The lachrymal thus forms the outer margin for the 

 so-called maxillary notch. The jugal is fused with the lachrymal 

 and is suturally united to the maxilla at the maxillary notch. It is 

 thus evident that the skull of the living genus Lipotes and that of 

 this fossil porpoise possess lachrymals which are essentially the 

 same both in shape and in relation to the surrounding bones. It 

 should be noted, however, that in this fossil skull the outer margin 

 of the maxillary notch is formed entirely by the maxilla. The distaJ 

 end of the lachrymal is very thin and is merely a wedge between 

 the anterior face of the supraorbital process of the frontal and the 

 maxilla. 



