394 CETACEA. 



which in this aspect is a shade larger than either liinder extremity of the cerebral 

 hemispheres. The medulla spinalis is relatiyely large, and set high in relation to 

 the cerebellum. 



Erom the foregoing description it would seem that Orcella has a delphin- 

 oid form of brain, comparatively massive, broad, and although in a general way 

 iiattish, yet by no means low set. The fronto-orbital lobes are unusually deep, and 

 the anterior brain-facies altogether vertically abrupt in contour. The cerebellum 

 is preponderantly large and in a great measure uncovered both laterally and above. 

 Moreover, as the sequel will show, the brain of Orcella manifestly differs in several 

 particulars from that of Flatanistay while it strikingly follows the general shape of 

 that of GloMcepJialus. 



Hxternal organs of generation (Plates XXXIII and XXXIV). — The cleft of 

 the vulva resembles that of other Cetaceans, the skin around being somewhat 

 smooth and pale coloured. The most characteristic feature is the existence of the 

 well marked peringeum (p^.) already mentioned, the raphe being about \\ inches 

 long, and in this particular, Orcella essentially differs from those whales which, 

 being destitute of pelvic bones, have no perineal space. 



The mammary slits (Plate XXXIII, fig. 1 m) are each 0'70 inch long and 

 situated 1*20 inch from the vulva, their hinder ends being 2*20 inches distant 

 from the anus. The nipple is not prominent, being laterally compressed and 

 placed at the base of the mammary furrow which is comparatively shallow, viz., 

 0*20 inch deep. 



The mammary gland (mg.) has an enormous dilated lactiferous sac, 2 inches 

 long, with a position immediately underneath the nipple. It runs horizontally 

 forwards, and into it all the lactiferous ducts open. The other portion of the gland 

 is very solid in character, flattened along the middle line, and in area has a length 

 of 9*50, a breadth of 3*25, and 0'25 of an inch thick. It is invested by a 

 strong fibrous capsule which is very firmly adherent to the gland substance, and is 

 with difficulty removed from it.^ 



The vagina (v) has the usual Cetacean characters, and has six as tincce. I 

 did not observe in the vagina of the gravid female any of those remarkable glands 

 which I shall have to describe in the gravid vagina of Tlatanista. 



Gravid uterus. — The mouth of the true os is a little to one side, which also holds 

 good with the lower os tincce, thus conferring a slightly spiral arrangement on the course 

 of the canal. The true os, when viewed from the uterine aspect (Plate XXXIII, 

 fig. 2), appears almost smooth, with only a few rudimentary folds, and in this respect 

 it materially differs from the os uteri internum of Flatanista (Plate XXXI, fig. 2), 

 and the Narwhal.^ In the gravid female the foetus was developed in the left horn, and 



^ See Hunter, I. c. : Kuhn, Ferussac, Bullet, des Sc. Nat. 1830, t. xxii. p. 322 : Rapp, Meckel's Archiv. fiir. Anat. 

 1830, p. 358 : Die Cetaceen Zool. Anat. dargestellt, 1837, p. 178 : Trail. Edinr. New Phil. Journ. 1834, Vol. xvii. pp. 117 

 et 363 : Is-GeofF. St. Hilaire, Ann. des Sc. Nat. 2 Ser. Zool. t. 1. 1834, p. 174 : Jacob, Brit, Assoc. Eeports, 1835, 

 p. 86: Astley Cooper, Anat. of Breast, 1839: H. Milne-Edwards, Le9ons. sur la Physiol., t. ix. 1870, p. 124, and 

 Turner, I. c. 



' Turner : Lectures on Placent. 1876, p. 50. 



