OF THE GREAT AUK, OR GARFOWL. 331 



upper contour of the solid prenarial part of the premaxillary : every other better cha- 

 racter of affinity is very closely repeated. 



The sternum of Alca tarda repeats the characteristics of that of Alca ivipennis, with 

 the exception of a notch on each side of the back part, 1 inch long by 3 lines wide. In 

 Alca (Phaleris, Temm.) psittacula, Pallas, the sternum is more dilated posteriorly, and 

 the notches are represented by oblong foramina of a wider form. The interorbital part 

 of the cranial roof is narrower, and the upper end of the lacrymal projects upward and 

 backward as a process. In Uria grylle (PI. LII. fig. 14), besides the posterior notches 

 (/) answering to those of Alca tarda, there is a small perforation, sometimes two 

 (ib. /',/"), on the inner side of each. 



The furcular and scapular arches oi Alca tarda closely correspond with those oi Alca 

 impennis. The coracoid is similarly perforated for a branch of the pectoral artery. 



The humerus closely agrees in shape and proportion ; the difference in the wing-bones, 

 in adaptive relation to the power of flight, of Alca tarda, begins to manifest itself in the 

 antibrachial bones, which are longer and less compressed than in Alcaimpennis, the ulna 

 also having a row of quill-pits or knobs : the bones of the head are shorter relatively to 

 the ulna than in Alca impennis. 



A closer resemblance is maintained between Alca tarda and A. impennis in the bones 

 of the pelvic limb, and is especially seen in the shape and proportions of the rotular 

 process, with its pro- and ecto-cnemial ridges, and in the proportions and attachments 

 of the fibula. 



The sum of the comparisons of the skeleton of Alca impennis with that in other Auks, 

 Phalerins, and Puffins, and also in Guillemots, goes to exemplify the close affinity of the 

 Garfowl to those sea-birds, and to indicate that it is a modified apterous member of the 

 AlcadiB. 



The Penguin, similarly apterous or with wings reduced to the function of fins, shows 

 its essential distinction from the Garfowl in all the flight-giving parts of the skeleton. 

 The number of vertebrae between the skull and sacrum is, indeed, the same ; but only 

 eight support moveable ribs, the total number of which is nine pairs, the last pair being 

 sacral. The atlantal hypapophysis is produced below into a compressed process ; the 

 anapophyses of the axis and two following vertebrae are mere tuberosities, not elongated 

 into processes. The pleurapophyses are styliform and produced backward in the third 

 to the tenth cervical, thence are shortened to the fourteenth, when the pleurapophysis 

 reappears as a separate styliform rib. The first four cervical vertebrce have each a 

 single posterior hypapophysis ; the sixth to the tenth inclusive have a pair of parapo- 

 physes simulating anterior hypapophyses. 



The parapophyses begin to project downward in the sixth cervical, increase in size 

 and convergence to the ninth, and at the tenth have a common median base, like a 

 bifurcate anterior hypapophysis ; in the eleventh cervical they disappear, and are 

 replaced by a true hypapophysis from the mid line of the under surface of the centrum : 



VOL. v. PART IV. 2 X 



