176 ESCHRICHT ON THE 



excepted, but tliey are usually the only parts of the skeleton by which the sex may also be 

 decided. 



In the toothed-whales the pelvic bones of the male are generally somewhat differently 

 formed, and, at least in some species, considerably larger in all dimensions, than those of 

 the female. This seems in a high degree to be the case with the killers, but it must 

 at the same time be admitted that their form is subject to many, even very surprising devia- 

 tions, as is clearly proved by their being often unsymmetrical with each other in the same 

 individual. 



They appear in all cases as a pair of bones much extended in length, having their posterior 

 extremities close upon the anus, and here approaching nearer to each other, but diverging from each 

 other in a forward direction, so as to have their anterior extremities twice as far removed from 

 each other as the posterior ones. They are more or less curved, with a concave often rather sharp 

 interior edge, and a convex and perfectly obtuse exterior margin. This general description of 

 the pelvic bones of the killers will especially hold true with respect to their hindmost two thirds. 

 In the foremost third they usually become much thinner, often almost cylindrical, and 

 end quite in front in an enlargement ; and it is principally in this part that differences of form 

 appear frequently even between the two bones of the same pair. 



I found these bones extraordinarily large and strong in Mr. Benzon's twenty-one and one 

 third feet long specimen, which was a male. They were 11^" long, and in the anterior 

 third but little more than 1" broad, in the two posterior thirds as broad as 2", besides 

 very thick everywhere. They were almost quite symmetrical with each other; the distance 

 between them in front was 10^", but in their most posterior and broader parts they are 

 bent towards each other in a uniform and slightly curved arch, so as to approach each other to a 

 distance of 4". The woodcut represents the outline of the left one seen from above.-' The 

 transition to the anterior more narrow third had the shape of a slight constriction ; there was 

 another and more considerable narrowing near the foremost extremity, which consequently had 

 a certain resemblance to the head of a rib. 



By examining the Orca skeleton of Nilsson at Lund, I found that its pelvic bones in nearly 

 all particulars resembled those of Mr. Benzon's specimen here described, only that they were 

 1" shorter, and considerably more narrow, being in the very broadest place only 1" 5'". 



As a contrast to the very large pelvic bones of these specimens, we shall now describe those 

 of Mr. Thomsen's thirteen feet long individual, which was a female. They were only 4|" long, 

 in their hindmost two thirds 5'" broad, and not perceptibly curved, but in theu* foremost only 

 3'" broad and almost cylindrical third they were bent slightly inwards so as to form a knee in 



^ All the pelvic bones represented here are given one fourth the natural size. 



