THE WHALEBONE WHALES OF THE WESTERN NORTH ATLANTIC. 129 



ABDOMINAL RIDGES AND FURROWS. 



In B. physalus the abdominal ridges and furrows are broader and less numer- 

 ous than in B. acuto-rostrata, much narrower and more numerous than in the Hump- 

 back. They are parallel for the most part, but anastomose frequently at different 

 points. Sars's description of the furrows in an European (Lofoten Ids.) specimen is 

 as follows (77, 13 and 14 sep.) : 



"The breast furrows, which are very characteristic of the fin-whales, occupy 

 the whole of the anterior half of the ventral side of the animal, from the tip of 

 the mandible to the navel. In the present species they are quite numerous 

 and extend well up on the sides of the body. In a straight line around the 

 ventral surface about 70 furrows may be counted. The middle ones extend far 

 backward to the very sides of the navel ; the others become little by little shorter 

 upward, so that the posterior boundary of the furrowed area on the sides forms a 

 line passing obliquely from the navel to the root of the pectoral fin. These fur- 

 rows as a whole run nearly parallel with the long axis of the body and each other, 

 but are often interrupted, so that a new one takes its origin a little in front 

 of the place where another ends. On the sides of the neck, or between the 

 corner of the mouth and the root of the pectoral, the furrows extend farthest up 

 on the side of the body, and their course is here less regular. From the corner of 

 the mouth, four short furrows run backward and are somewhat sigmoid, and one 

 approaches near the root of the pectoral. From the root of the mandible run 8 

 furrows of unequal length, which converge posteriorly without reaching the root of 

 the pectoral; they thus lie between the lowest of those from the corner of the 

 mouth and the first which runs forward from the root of the pectoral, with which 

 the furrow following most closely takes a quite strongly curved course. At the 

 root of the pectoral fins both above and below are a number of short strongly 

 curved furrows." 



In the Newfoundland specimens the arrangement of ridges and furrows was 

 the same, as will be seen on examining pis. 8 and 9. The number and course of 

 the farrows are, however, subject to considerable variation. In some cases the fur- 

 rows in the root of the mandible are continuous with those running forward from 

 under the pectoral, and form one series with them. One or two pairs directly on 

 the median line of the throat are shorter anteriorly than the lateral ones, so that 

 there is quite a large plain area immediately under the tip of the mandible. 



The total number of furrows between the two pectorals varies considerably in 

 different Newfoundland specimens, as follows: No. 1, about 80; No. 2, 62; No. 7, 

 72 ; No. 13, 78 ; No. 4, 56 ; No. 9, 62 ; No. 20, 76. These totals were obtained by 

 counting from the median line to the root of the pectoral on one side and multiply- 

 ing by two. The average is the same as in Sars's Lofoten Ids. specimen. 



The breadth of the ridges in the vicinity of the middle of their length in New- 

 foundland specimens was 2 in. to 2 in., but at the posterior ends they increased 

 in breadth to 4 inches. The breadth of the furrows depends chiefly on the pressure 

 exerted from the interior of the body, though they do not always close together 

 when this pressure is withdrawn. In the dead animal, the weight of the integu- 

 ments which happen to be nearest the ground pulls the ridges which are higher up 



