ON THE BEPEODUCTION OP CERTAIN SPECIES OF ICHTHYOSAmUS. 75 



towards that of the large individual in which it is contained, as is the 

 case with the other specimens which I have described. The head is 

 directed downwards, and the snout extends beyond the limits of the ribs, 

 as though it were just protruding from the body. The extremity of the 

 snout is imperfect, but the head, as preserved, is 9 inches long. The ver- 

 tebral column has a total lengtKseeu of 20 inches, but may extend further 

 under a rib. The vertebras are in natural sequence, though the caudal 

 region is bent round in a curve veutrally ; but it is difficult to say whether 

 this is the position natural to the embryo. The dorsal vertebris are ^-inch 

 in diameter, and the corresponding centrums of the large animal are 

 2^ inches in diameter. The ribs of the young animal are preserved, and 

 there are bones which appear to be coracoids. The hind limb is distinctly 

 preserved, and measures 1^ inch in length. The femur is |-inch long, and 

 the smaller limb-bones are in three rows. It is unfortunate that the hind 

 limb of the parent is not available for comparison, but that portion of 

 the original slab is missing. So far as it is possible to compare the 

 pointed snout and teeth of the young with the large animal, there is 

 nothing to suggest that they belong to different species. 



After thus detailing the facts as to the position and character of these 

 specimens, the conclusion to be drawn from them may be left to a con- 

 sideration of the cumulative evidence of the figures ; and if I do not for- 

 mally discuss the view which Prof. Quenstedt has adopted, that these 

 specimens were eaten, it is because no other animals except Ichthyosaurs 

 have ever been found in the hinder part of the abdominal cavity of large 

 .specimens of this genus ; and because the remains of fishes and cuttles, 

 which appear to have constituted the ordinary food of these sea-monsters, 

 are always found, comminuted and indistinguishable in form, in a more 

 anterior position. It is improbable that the large animal, with its com- 

 paratively firm quadrate bones, would have been capable of swallowing 

 a creature in which the head, as in the first Tiibingen specimen, was 

 more than two-thirds the length of its own head, without in any way 

 crushing or breaking the structure, or even disarranging an eye-plate ; 

 while the evidence from the structure of coprolites seems to me to render 

 superfluous any further discussion of this question of the young animals 

 being in process of digestion. That the small specimens were washed in 

 a dead state into the already dead bodies of the large specimens is a 

 hypothesis that can need no discussion ; for the many cases in which the 

 two bodies are parallel, with the smaller placed entirely within the larger, 

 have no appearance of accident, while a movement of the sea which would 

 wash the young about in such a way would probably scatter the bones of 

 both animals. 



I therefore submit that the evidence indicates that these Ichthyosaurs 

 were viviparous, and were probably produced of different relative bulk 

 in different species ; and it may be from feeble health of the parent 

 or from some accident of position in the young that they were not 

 produced alive, and thus have left a record of their method of reproduc- 

 tion to which no allied extinct group of animals has shown a parallel. 

 There is some evidence that in certain cases many young were produced 

 at a birth, and although the specimens are not in the best state of preser- 

 vation, analogy strongly suggests that this is a distinctive character of 

 certain species. It cannot be taken as proved that all Ichthyosaurs were 

 viviparous ; for the character, though met with among fishes, amphibians, 

 and reptiles, is not distinctive of any living order of these animals ; and it 



