go SnvFF.LDT, Osteology of Hayris's Cormorant . [isf' 



Oct. 



for the articulation of thie occipital style. The occipital lines 

 meet each other in the middle line, several millimeters anterior to 

 this facet, in the interparietal crest. There may be a rudimentary 

 pars plana present on either side, and the maxillo-palatines con- 

 siderably developed. Transverse frontal area on superior aspect 

 of cranium, between the orbits, broad. This is the group or type 

 to which Nannoptenmt harrisi belongs. 



Passing to the third group, which may be designated the carbo 

 type, we find the superior mandible to be much shorter. The 

 cranium is large and strong, exhibiting no vertical compression, 

 nor is it especially broad. The foramen magnum is much 

 smaller, both actually and relatively, than it is in the two fore- 

 going types, and the cranio-facial hinge is more or less inflexible. 



Lastly, we have the perspicillatits type, in which the cranium 

 is compressed from above, downward to some degree, very broad 

 and thick. Pars plana is better developed ; the great vacuity in 

 the anterior wall of the brain-case, present in all the other types, 

 is here vertically divided in the middle line by a slender bar of 

 bone. The cranio-facial hinge is more mobile, and, as in the 

 types two and three, the squamosal and post-frontal processes 

 are developed, especially the latter. These are practically absent 

 in the Urile type of skull. The occipital crest and occipital line 

 are more separated, as in the penicillatus and carbo types. 



Lucas, in his description of P. perspicillatus, states, and I repro- 

 duced the statement in my " Osteology of the Steganopodes," 

 p. i68, that " the absence of external narial openings is also a 

 secondary character, for the young Cormorant possesses perfectly 

 open nostrils, while the cranium is almost as schizorhinal as that 

 of a Gull. As growth proceeds the narial openings become more 

 and more restricted, until, about the time (the exact time is un- 

 certain) that the young birds take to the water, not only the 

 external openings, Init those of the cranium, have become com- 

 pletely filled."* 



While the nostrils are obliterated in all adult Cormorants, in so 

 far as the superior mandibular theca is concerned, I very much 

 question that they are entirely obliterated in the osseous mandible 

 of the skull ; they certainly are not in any of the skulls now before 

 me — that is, if the more or less conspicuous foramen at the 

 posterior ending of the nasal groove passing down the lateral 

 aspect of the superior mandible on either side does not represent 

 what remains of these openings. In some skulls 1 find a second 

 and smaller foramen at some little distance in advance of the one 

 here referred to. It also lies in the track of the nasal groove, and, 

 as in the case of the large one, leads directly backward into the 

 rhinal chamber, just as the narial passage would do were it 

 present. Moreover, the larger and more posterior of the two 

 foramina, when two are present, is always situated at the anterior 

 margin of the nasal bone where the avian nostril commonly 



* Lucas, F. A., Proc. U.S. Nat. Mus., 1889, pp. 8.S-94. 



