486 PROFESSOR TURNER ON THE GRAVID UTERUS AND 



comparatively thin cuticle. Parallel to and immediately below the base of the 

 dorsal fin, the dark-slate colour was modified by a lighter pinkish-tinted patch, 

 which corresponded with the purplish spot represented by Schlegel in the 

 adult Orca which he has figured." 5 ' The foetus measured from the tip of the 

 upper jaw along the middle of the back to the mesial notch of the tail 36 

 inches. Its greatest girth midway between the root of the flipper and the 

 attachment of the umbilical cord was 18^ inches. From the attachment of 

 the cord to the root of the penis, 3*5 inches ; from the latter to the anus, 2'0 

 inches ; and from the anus to the mesial notch of the tail, 103 inches. From the 

 tip of the lower jaw to the umbilical cord, 152 inches. Length of pectoral fin, 4*8 

 inches ; length of base of falciform fatty fin, 3 2 ; height measured along 

 anterior border, 4*2 inches. From posterior rise of dorsal fin to mesial notch 

 of tail, 14-2 inches. Between tips of tail lobes along their posterior concave 

 borders, 7 5 inches. 



Comparison of Placentation with that of other Mammals.f — I shall endea- 

 vour, in making this comparison, to show, as far as the materials at my disposal 

 will permit, the features of resemblance and dissimilarity, not only as regards 

 the general arrangement of the foetal membranes and uterine mucous surface, 

 but their more minute structure. 



The dissection of this Orca confirms the results previously arrived at from 

 the dissection of various specimens of the genus Detyhinus, by the anatomists 

 quoted in my introductory observations, that in the cetacea the chorion extends 

 into both uterine horns, and its surface is so studded with villi as to form a 

 placenta of the " diffused" type, in which, from the absence, so far as was 

 ascertained, of a uterine decidua intermingled with the chorionic villi, the foetal 

 and maternal surfaces readily separate from each other. It also agrees with 

 the specimen examined by Professor Rolleston, in the presence of a bare spot, 

 free from villi, at each of the poles of the chorion. But I have also demon- 

 strated, what had previously been overlooked, that a third, larger, non-villous 

 area is situated opposite the os uteri internum. 



Of the mammals, the placentation of which most commonly comes under 

 observation, the sow and the mare also offer well-known examples of the dif- 

 fused form of placenta. Of these the uniparous mare presents more points of 

 resemblance to the uniparous cetacean than does the pluriparous sow. For in 

 the mare not only does the chorion of the solitary embryo extend from one uterine 

 cornu to the other, and possess small non-villous spots at the poles, but an 

 even larger, stellate, bare spot also exists in relation to the os internum. J 



* Abhandlungen aus dem Gebiete der Zoologie und vergleichenden Anatomic Part ii. fig. 7. 



t October 1871. This section and the final one, entitled "Physiological Conclusions," have 

 been re-written since the Memoir was read. 



I In one specimen, I observed that the non-villous pole of the horn of the chorion which contained 

 a foetal foal about 2 feet long, was somewhat smaller than that of the Orca, but the bare spot in the 



