12 PROCEEDINGS OF THE NATIONAL MUSEUM vol. GO 



Eurhinodelphis cristatus}'' In this specimen from the Calvert cliffs 

 the maxilla does not completely sheath the anterior margin of the 

 supraorbital process. The outer margin of the frontal plate of the 

 maxilla is very irregular above the orbit, but on both maxillae there 

 is a deep indenture which sets off a process comparable to that shown 

 on the skull oi E. cocheteuxi. This portion of the maxilla, however, 

 does not project beyond the anterior edge of the supraorbital process 

 to any appreciable extent, but it may show how a process like that 

 present on the E: cocheteuxi skull was formed. In front of and 

 below this process there is a small bone which is continuous ventrally 

 with what was considered by Abel to be the lachrymal. This bone 

 is fused with the jugal and is closely appressed to the maxilla. 

 Differences in respect to the size and position of such bones are to 

 be expected in different genera, but it may appear somewhat unusual 

 that such modifications should be present in different species of the 

 same genus. The anterior end of the jugal is not visible from a 

 dorsal view. 



The frontals are limited to a narrow strip on the vertex, being 

 overspread by the premaxillae and maxillae laterally, and by the 

 nasals anteriorly. Posteriorly they abut against the supraoccipital 

 and intervene between the extremities of the maxillae and the latter. 

 Anterolaterally and at a lower level than the vertex each frontal 

 sends out a supraorbital process which forms a complete osseous 

 roof for the orbit. No trace of a small bone described as the inter- 

 parietal could be found on this skull. 



The nasals are small semipyriform bones placed obliquely between 

 the posterior extremities of the premaxillae, with their anterior 

 portions in contact along their inner margins. In position they 

 agree with those of Eurhinodelphis cocheteuxi^ although in general 

 outlines they are somewhat different. They do not overhang the 

 nasal apertures. 



Lateral view. — Aside from the relative small size of the braincase 

 the skull (pi. 2) is characterized by a shallow temporal fossa which 

 is roofed over for the most part by the maxilla and the lateral 

 extension of the frontal, a wide orbit, and a long zygomatic process. 

 The rostrum is exceedingly long and slender, depressed proximallj'', 

 and compressed from side to side anteriorly. To compensate for 

 strains arising from the length of the rostrum the posterior ex- 

 tremities of the maxillae are expanded horizontally. Additional 

 strength is given to the rostrum by the almost complete ankylosis 

 of the maxilla and premaxilla, as well as by the anterior extension 

 of the vomer. 



" Abel, O., Mem. Mus. roy. d'hist. nat. de Belgique, Bruxelles, vol. 2, p. 15, fig. 1, 1902. 



