48 BAUR. [VOL. I. 



Among eleven skeletons Reinhardt ('73, pp. 221-228) found 

 three with three sacral vertebrae. 



1. Caiman sclerops Schneid. The last lumbar is transformed 

 into a sacral. There are only 23 presacral vertebrae. 



2. Crocodilus americanus Laur. (acutus Cuv.). There are 

 three sacrals; the first two are the normal; the first is concave- 

 plane, the second plane-plane, and the third plane-convex; 

 all the following are procoelous, and the first bears a chevron. 

 The first caudal has been taken up by the sacrum. There are, 

 however, only 23 presacral vertebrae. 



3. Crocodilus americanus Laur. Three sacrals. The first 

 caudal is transformed into a sacral vertebra, and there are 24 

 presacral vertebrae. 



4. Another case with three sacral vertebrae has been described 

 by Case ('96, pp. 231-233). There are 24 presacral vertebrae. 

 The 25th has the sacral ribs inclined backwards and becoming 

 slender. The 26th has strong thick ribs; and the 2/th has 

 also well-developed ribs articulating with the ilium. This ver- 

 tebra is seemingly biconvex. The first chevron is attached 

 between the 28th and 29th. The first caudal has been taken 

 up into the sacrum. Both sides are symmetrical. 



5. I have described a case in Alligator mississippicnsis Baud. 

 The last lumbar possesses small sacral ribs, which, however, 

 do not reach the ilium. In front of this there are 23 presacral 

 vertebrae ('86, p. 690). 



6. Crocodilus americanus Laur (acutns Cuv.), No. 129, B. 

 Museum, Cambridge, England. The 25th vertebra has a 

 strong presacral rib on the right side; it is much weaker on 

 the left, and united with the center. The 26th shows typical 

 sacral ribs; the 2/th bears on the left side a strong free sacral 

 rib, on the right side a weaker rib but free. The ilium is sup- 

 ported on the left principally by the 25th and 26th, at the right 

 by the 26th and 2/th vertebrae. The 28th is biconvex. Here 

 we have an asymmetrical sacrum. This case was published 

 by me in 1889 ('89, p. 240). 



7 and 8. In two specimens of Crocodilus porosus Schneid. 

 (biporcatns Cuv.) in the Reichsmuseum of Leyden there are 

 only 23 presacral vertebrae ('89, pp. 240, 241). 



