ON THE HKPEODUCTION of certain species 01' ICIITIIVOSAURUS. 73 



can be defined with the same accuracy and certainty as characterises 

 other kinds of palisontological work. 



The specimen in the Royal Museum at Stuttgart (fig. 4) wants the 

 head and the hinder half of the tail, in which the vertebrje become greatly 

 attenuated. The portion of the animal preserved is aboiit 5 feet long, and 

 of this length rather less than two- thirds is comprised by the body region 

 of the animal, in which dorsal ribs are developed. The fore limb lies some- 

 what bent on the ventral margins of the ribs, and the hind limb is well 

 preserved below the pelvic region. From the apparently firm union of the 

 ribs to the dorsal centrums they have been pulled somewhat apart, and do 

 not approximate towards their ventral edges. This animal lies upon its 

 left side, inclining a little towards the back. As usual there is an upward 

 arch of the anterior half of the dorsal region. The young animal lies in 

 the abdominal cavity, and, although not perhaps so fully developed as 

 might be, its length, so far as can be made out, appears to be about 

 2 feet 6 inches. The vertebral column is parallel to the vertebral column 

 of the large animal, and is separated from it by an interspace of 2^ inches in 

 the posterior region of the large animal, becoming anteriorly a little farther 

 distant from it. The young animal lies upon its right side, and although the 

 ribs have been strained from their natural position, the young animal is 

 still entirely between the ribs, except where a few of them have been 

 purposely removed, the better to show its characters. The head of the 

 small animal is about 10 inches long, and rather more than 2^ inches 

 deep at the hinder border of the orbit. The snout projects from the 

 abdominal cavity in the region of the pelvic bones for about a third of its 

 length, but the pelvic bones are no longer in situ, owing to the conditions 

 of fossilisation. The dorsal region of the young specimen has not been 

 so developed as to show its ribs, but the vertebral column is in sequence, 

 though the pressure of the overlying ribs of the large animal has some- 

 what broken the chain, and exposed the faces of one or two of the few 

 vertebrae, the lai'gest of which in the lower dorsal region has a diameter 

 of half an inch. The depth of the body of the young animal was appa- 

 rently 4^ inches. The extremity of the tail is not seen. It may be noticed 

 that the ribs of the lai'ge animal extend over the eye and nasal region of 

 the left side of the young head, but the shortening of the ribs on the left 

 side of the large animal shows that the snout could hardly have been con- 

 tained entirely within the pelvic cavity if the young animal occupied its 

 present position during life. It is of course jjossible that there may have 

 been some slight shifting of position ; but the presence of the abdominal 

 ribs of the large animal in situ, and the generally undisturbed character of 

 the remains, lead me to believe that the relative positions of the two indi- 

 viduals are not now greatly difi'erent from what they were during life. 



I can only endorse the conclusions of Von Jaeger that we have here a 

 fcetus in the act of being expelled, and although the size of the young 

 animal is relatively large, it is not unparalleled among living amphibians ; 

 and the eggs of birds vary so much in bulk, that with gigantic eggs, such 

 as those of .(3Epiornis, the large size of this embryo is not unexampled. 

 The great extension of the young in the body of the parent need perhaps 

 present no difficulty when we remember the large space occupied by the 

 ovarian organs in the lowgr vertebrata; and, large as the young animal is, 

 there is no known limit to the capacity for expansion of the oviduct which 

 would render its size and position improbable on such an explanation. If 

 it were asked why the old animal should have died, I can only state that 



