« AnteriorContinuar »
There is, as already stated, considerable variation, the cause of which is not entirely clear. This variation affects the American specimens, which I have endeavored to measure in a uniform manner, nearly as much as the European specimens, the measurements of which are collected from various sources,
The measurements of the Taranto (Italy) whale given by Gasco in the text of his article (47) do not agree with measurements taken from his figures, and measurements from the different figures do not agree with one another. Furthermore, Capellini's measurements of the same specimen do not altogether agree with Gasco's. Guldberg's measurements of the Iceland skulls also lack conformity to a consider. able degree. While these differences may be partially due to different methods of measurement, it can hardly be supposed that they all arise in that way. This explanation does not serve in the case of my own measurements.
It seems probable that the discrepancies are in part due to the shrinking and warping of the various bones of the skull. The long, slender maxillæ and premaxillæ, the long orbital processes of the frontals and maxillæ, seem quite easily subject to such distortion, and in some skulls it can readily be seen that warping bas taken place. Again, it should be observed that most of the skulls are those of young individuals, and probably exhibit differences of proportions correlated with different stages of growth. Aside from all this, however, it is undoubtedly true that the species shows a considerable individual variation in proportions.
The measurements of the length of rostrum in Guldberg's skull, received from Capt. Amlie, and in Capt. Berg's No. 2, are from the base of the same and not from the posterior margin of the maxilla, as in other cases. This accounts for the diminished length. The measurement of the rostrum of the Taranto whale was taken from Gasco's figure of the upper surface of the skull (47, pl. 2, fig. 1); but it is obvious on comparing this figure with the side view that the rostrum is too short in the former. A measurement from the side view gives about 77.2 % for the length of the rostrum, which is no doubt more nearly correct.
Gasco's measurements of the mandible of the San Sebastian whale of 185+ are “from the point of meeting of the internal lateral margin with the inferior margin of the condyle,” which accounts in part at least for the much smaller proportion.
The other discrepancies, affecting the breadth of the skull across the orbits, the length of the mandible, and the distance along the curve of the premaxillæ, from the tip of the vasals to the tip of the premaxillæ, cannot be so readily explained. As they occur in both the American and the European series, however, they cannot be regarded as indicating specific differences. Doubtless, many of them would disappear if the various specimens could be brought together for actual comparison.
CHARACTERS OF THE VERTEBRA.
Measurements of the vertebræ and other parts of the skeleton in a few European and American specimens are given in the following table:
Gasco has given figures of many of the vertebræ of the Taranto (Italy) skeleton (47, pls. 3, 5, 7, 8), in which the outlines are taken from photographs. These figures I have compared with the Long Island (N. Y.) skeleton in the National Museum, No. 23077, and find a most complete agreement, except in one or two
In the figure of the 4th lumbar of the Taranto skeleton (vertebra No. 24) the anterior zygopophysis is much smaller than in the Long Island skeleton, and the posterior margin of the base of the neural arch is much more curved. In the side view of the 1st lumbar of the Taranto whale (vertebra No. 21) the transverse process is represented as having a peculiar shape and direction which is not evident in the front view of the same vertebra, and is not found in the Long Island skele. ton. The sixth caudal (vert. No. 39) of the Taranto skeleton is represented as having only a shallow emargination inferiorly, while in the Long Island and other specimens the emargination is very deep and the anterior and posterior margins come close together, foreshadowing the formation of the foramen which is found in the posterior caudals. There is every probability that this figure is incorrect, or that the vertebra is imperfect below. All the vertebræ of the Taranto skeleton are figured without the epiphyses, and hence appear thinner than they otherwise would.
10 Twice 12.
1 From figure.
The points in the vertebral column at which the several processes and foramina appear or disappear furnish data of considerable importance in the comparison of species. These data are brought together in the following table:
BALÆNA GLACIALIS BONNATERRE. AMERICAN AND EUROPEAN. VERTEBRAL CHARACTERS.
It is much to be regretted that so few data relative to European specimens have been recorded. In so far as they are available for comparison, the agreement with corresponding data from American specimens is very close.
The chevron bones are figured or described in the case of one or two European skeletons only. Graells's figure of the Guetaria skeleton (52) shows 12 chevrons, the first smaller than the second and somewhat pointed. Gasco states that the Taranto skeleton has 10 chevrons, but that some were probably lost.
Of the American skeletons, those in the Field Columbian Museum and in the Museum of Comparative Zoology, have 9 chevrons each. In both cases the first is attached to the posterior end of what is really the second caudal vertebra, so that the skeletons appear to have one more lumbar vertebra than they should. In the skeleton in the former museum the first chevron in position is small, but in the skeleton in Cambridge it is the largest of the series. In this case it is therefore probably the second chevron. The Charleston skeleton has 10 chevrons, but there were probably more originally.
The number of pairs of ribs is 14 in all European and American specimens, except the San Sebastian skeleton of 1854, and in this also, although 13 pairs are
Right side only.
· Left side only.
. Or 42d.
assigned to it by Gasco, he expresses the opinion that there may originally have been 14 pairs.
In the majority of specimens the first rib is single-headed, but in the Guetaria (Spain) skeleton, that of the right side shows a small secondary process adjacent to the proximal end. The bifurcation is also found in the San Sebastian skeleton of 1854. Gasco's description of the first pair of ribs in this specimen is as follows:
“No doubt the first pair of ribs of the young whale of San Sebastian, placed opposite the corresponding parts of the Taranto whale, exhibit certain singular differences, which though they do not surprise us at present, led J. E. Gray to create the genus Hunterius, a genus which no one now accepts. The superior or vertebral extremity of the first pair of ribs is bifurcated. In the right one the bifurcation extends 55 mm., but in the left does not surpass 15 mm. In the left, the part of the rib which thus separates, 15 mm. long, terminates acutely and may be compared to a little horn, which has the apex distant scarcely 2 cm, from the internal border of the rest of the rib, and about 7 cm. from its superior extremity. Its circumference is 45 mm., and at the apex, 25 mm. On the other hand, on the right the portion of the rib which is separate is 55 mm. long. It is somewhat thicker, the termination obtuse, and it is distant its whole length only 3 or 4 mm. from the inner margin of the rest of the rib. So it may even be suspected that in the progress of time this portion might be completely fused with the rest of the rib." Its apex is distant from the superior extremity of the rib only 2 cm. Its circumference at the base is 8 cm., and 9 cm. near the apex. All these relative differences in the degree of bifurcation in the same individual indicate clearly bow little of importance there is in the separation of a portion of the rib.” 1
The distal ends of the two ribs constituting the first pair are commonly unequal in breadth. In the different specimens the measurements are as follows:
'Annal. Mus. Civic, Genova, 14, 1879, pp. 606, 607.
Type of B. cisarctica.
In the majority of specimens the last pair of ribs is much shorter than the penultimate pair, but in the Raleigh Museum skeleton the last left rib is nearly as long as the rib which precedes it. The right rib is shorter.
Among European specimens the sternum appears to have been figured only in the case of the Taranto skeleton and Guldberg's Iceland skeleton No. 1. These
BALÆNA GLACIALIS BONNATERRE.
Fig. 85.–TARANTO, ITALY. (From Gasco.) Fig. 86.-ICELAND. (From GULDBERG.) Fig. 87.—LONG ID., New York. (AMER. Mus. Nat. Hist.) (FROM A SKETCH.)
two sterna (text figs. 85 and 86) show little resemblance to one another at first sight; nevertheless, it will be perceived that if that of the Taranto skeleton were lengthened posteriorly it would approach that of the Iceland specimen, the form in both cases being rudely heart-shaped.