21 



2.310 fem. (measured in a straight line from the apex of the 

 lower jaw to the extreme point of the tail fin) the 95 centim. 

 long foetus might in that case be regarded as quite full-grown, 

 for its length amounts to more than V:i of that of an ordinarily 

 large female "White-side. It may probably, however, be assumed 

 that the size of a newly-born young one of this species, as 

 of the Phocæna, is more than '/s the length of the mother 

 animal. If the 95 centim. length be taken as the basis of 

 calculation, the size of the new-born animal is -/s that 

 of the mother, and we may perhaps add, that the female 

 foetuses are somewhat smaller than the males, just as the 

 full-grown males are larger than the full-grown females. Tiiere 

 are, of course, also variations in the size of new-born animals 

 of this species, as there are of other species of Mammals. 



As the 842 millim. long fo'tus was in the best state of 

 preservation, and drawings were therefore made of it, it will be 

 the subject of the following description. 



Proportions. The head is 'i^i/. of the length of the 

 body, the pectoral tins '/o (from '/\.v to Vs. 4 i» the other 



foetuses), the dorsal tin between Vin and 



/u 



of the lenffth of 



the body. 



The head. The front part of the facial region, "the 

 beak", is well developed, but reveals its fcetal age by the 

 rounded shape; there are 6 or 7 fætal hairs to be counted 

 on each side above the mouth fissure. The 112 millim. long 

 upper lip is straight but for a slight sigmoid curvature, a rather 

 downward-tending convexity in the foremost part. In front, 

 at the median line, the upper lip describes a little descending 

 curve, answering to a depression in the apex of the lower jaw. 

 The furrow between the "beak" and the upper part of the face 

 is deepest in front, on both sides of the median line. The 

 95 centim. long tVetus also shows liere. in the middle, a little 

 l)reak or larger concavity, so tliat the upper contour of the 

 head which forms a gentle convexity from the crown downwards 

 over the front, here becomes a concavity marking the boundary 

 between the "beak'" and the facial region above it, and then 

 describes a convex curve to the apex of tlie upper jaw. The 

 shape of the lower lip is sigmoid, with the greatest concavity 

 above in the middle (cf. tig. 1, p. 21). Its foremost end projects a 

 little beyond the apex of the upper jaw. Within the lip, between 

 it and the dental series, there is a long keel, which becomes 

 broader until it loses itself at the back. In the slightly open 

 mouth can be seen the anteriorly free tongue with its fringed 

 edge. — The eye fissure (I2V2 millim. long) lies a little 

 above (12 millim.) the angle of the mouth, and about 22 millim. 

 behind it. There has been no relative change in the level of 

 the eye region. — The ear aperture, about ' j millim. in 

 diameter and at a distance of 14 millim. from the hinder angle 

 of the eye. lies a little lower than the cleft of the eye, but 

 above the continuation of the mouth cleft backwards. — The 

 nasal aperture now presents its peculiar semilunar form, 

 with the convexity turned forwards. The frontal plane through 

 the back of the blow-holes almost intersects the anterior angle 

 of the eye. 



Fig. 1. 

 Lagenorhynclius acutiis, Gray, Foetus 842 millim. lonf. 



