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Show 46 ON THE ANATOMY OF CERTAIN AUKS. [Jan. 18, longer and narrower than they are in B. marmoratus, and with more pointed extremities. In S. antiquus, too, the connecting band of hepatic tissue, joining the two lobes at the back and above, is far more extensive than it is in B. marmoratus; I fail to find any trace of a third lobe in either of these Auks. Both of these Murrelets possess a large pear-shaped gall-bladder, lying, in either case, beneath the inferior edge of the right lobe of the liver. Likewise in each is the spleen well developed; but this organ in S. antiquus is long and subcylindrical in form, while in B. marmoratus it is shorter, thicker, and of a decidedly pyriform outline. Macgillivray gives us a very good description, illustrated by three figures, of the proventriculus and gizzard of the Little Auk (Mer-gulus aile), which appears in the eighth volume of Audubon's ' Birds of America,' the royal quarto set. In the birds before me I fail to find the hand of " glandules," arranged as a belt at the extremity of the proventriculus, at the entrance of the stomach. Nor is the oesophagus so thin as Macgillivray found it to be in M. aile : in other particulars, however, these Auks seem to be quite similar to it; for I find the inner coat of the elongated proventriculus and the lower part of the oesophagus thrown into strong longitudinal rugse or folds, among which the surface is thickly studded with minute openings, which I take to be the mouths of the glandules. These rugae are continuous with similar, longitudinal elevations in the gizzard ; but in this latter cavity they are covered by a closely fitting corneous structure that readily peals off in the alcoholic specimens, leaving the rugae in a condition precisely as we find them in the proventriculus and oesophagus. The gizzard and proventriculus are continuous and but faintly marked externally by a constriction which shows the ending of the latter and commencement of the former, while internally, as I say, the definition is made quite sharp by the corneous layer of the gizzard. The disposition of the muscles of this latter organ are somewhat differently arranged from what Macgillivray gives us in his figure of M. aile. The tendon from which the fibres radiated in the Murrelets above described is situated quite laterally, and nearly opposite the pyloric exit of the pouch ; while in Macgilli-vray's drawing of the Little Guillemot, already referred to, this gastric tendon is centrally located as we see it in Pigeons and other birds. Both of m y specimens had entirely empty gizzards, the cavities not even containing a few grains of coarse gravel, which is not au uncommon thing, I believe, in certain Auks. The intestines of these Murrelets present us with nothing worthy of special remark, and I find a well-developed and large pancreas present in each. According to Macgillivray, in M. aile the rectal extremity of the intestinal tube becomes much enlarged and quite globular, while a short distance above it we find a pair of caeca of no great size. Unfortunately an accident happened to these parts in both of m y specimens ; but I presume much the same arrangement would obtain, as, so far as I know, all Auks are thus constructed in regard to this part of their economy. If hereafter the differences I have pointed out are found to be |
