228 



DESCRIPTION OF A SPECBIEX 



whether viewed under a physiological or classificatoiy point of view, sometimes vary in the 

 individuals of the same species. lam convinced that the most experienced naturalist would 

 be surprised at the number of cases of variability, even in important parts of structure 

 which he could collect on good authority, as I have collected during a course of years." 

 "Wide-ranging, much-diflfused and common species vary most." "Species of the larger 

 genera" (that is, those having the greater number of species) "in each country vary more 

 frequently than the species of the smaller genera." Now, according to Prof Van Bene- 

 deu, all the tinners are included in one genus — Bcdcenoptera, which is spread throughout 

 the seas, and comprises several species. The B. miiscuhis is probably the largest species 

 in point of numbers, and likewise the most widely spread, and consequently the one present- 

 ing the greatest variations. Distinctions based on the bifurcation of the first rib have been 

 shown by Van Beneden, and subsequently more in detail by Mr. Turner ^ to be of very lit- 

 tle value. 



It now remains to show how much variation exists by comparing the Boston skeleton 

 and several others one with another. Before dissection the chief peculiarity was the thick- 

 ness of the body in proportion to its length ; this may partly have been due to distention ; 

 but the cranium was very uncommonly large, forming a fourth of the length in the flesh, and 

 naturally more in the skeleton. Mr. Flower's drawing in the Proc. Zool. Soc, 1869, repre- 

 sents not only a more slender animal, but one with a more solid and projecting lower jaw. 

 The drawings and measurements of the so-called P. Duguidii represent a very narrow body 

 and beak ; the flippers are rather longer in proportion. Slight differences in the position 

 of the anterior limb and the dorsal fin are to be found by comparing the measurements of 

 several individuals, but nothing worthy of particular notice. 



On comparing the upper aspect of the skull (PL vi, fig. 1) with that in Van Beneden and 

 Gervais' " Osteographie," with that in " Recent Memoirs on the Cetacea " by Eschricht, 

 Reinhardt and Lilljeborg (Ray Society, 1866, PI. iii, fig. 3), with that of Eschricht's 

 Nordhval and the Rorqual de la Mediterranee in Cuvier's Ossemens Fossiles, I find that 

 though in several points resembling each, in others it differs from all ; it is perhaps most 

 like the last mentioned. 



The diversity of the proportions of the breadth of the skull and of the beak to the 

 length of the skull, the latter being taken as one hundred, is very well shown iu Mr. 

 Flower's table, Proc. Zool. Soc, 1864, p. 399. In the following table I reproduce his cases 

 of the P. antiquorum, adding to them those of the animal taken at INIargate, and described 

 by him Proc. Zool. Soc, 1869, three from Lilljeborg's Scandinavian Cetacea and the Boston 

 Whale, calculating the proportions in the same manner, but omitting fractions. 



PKOPOETION TO LENGTH OF HEAD. 



Specimen. 



Antweip. 



Louv.ain. 



Alex.inclra Park. 



Roshei'ville Gardens. 



(Young) Leyden. 



(Young) Mus. R. Coll. Surg. 



Specimen. 



INIargate. 



Chiistiania. 



Bergen. 



Young (described by Companyo) 



JBoston. 



Average. 



Breadth 

 of Skull. 



44 

 45 

 47 

 37 



46 

 45.81 



Breadth 

 of Beak, 



17 



19 

 19.25 



'Journal of Anatomy and Physiology, vol. v. 



