Reviews — Dr. E. Fraas on Ichthyosaurus. 



517 



Zoologists commonly regard the Ichthyosaurian modification among 

 reptiles as equivalent to that of the cetacea among mammals ; and 

 it is very interesting to find how remarkably dolphin-like is the 

 restoration of Ichthyosaurus given by Dr. Fraas. There is a tri- 

 angular dorsal fin, and also a large caudal fin ; while a row of 

 horny excrescences extends along the back from the former to the 

 latter. Ichthyosaurus, however, difi'ers essentially from the dolphins 

 in having the great caudal fin vertically, instead of horizontally, 

 extended. The vertebral column is continued to the point of one 

 lobe, as in a heterocercal fish ; but Dr. Fraas supposes that this was 

 not the upper lobe (as in fishes), appearances suggesting rather that 

 it was the lower lobe. In propoi'tion to the size of the animal this 

 fin is very large, and Dr. Fraas' discovery is an interesting confirma- 



Skeleton of Ichthyosaurus exhibiting the contour of the integument, 

 with an outline -restoration of the same. 



tion of the surmise of Sir Richard Owen, who, many years ago, 

 noticed the frequent dislocation of the tail of Idithyosanrus at a 

 fixed point, and could only explain the circumstance as due to the 

 weight of a caudal fin dragging upon this part of the body after death. 

 As yet the specimen described by Dr. Fraas is unique, and some 

 points in his interpretation of the fossil may perhaps admit of move 

 than one view. We can only hope that further evidence will soon 

 be forthcoming, and meanwhile expi-ess our appreciation of the 

 enthusiasm and success with which Dr. Fraas is prosecuting his 

 researches among the Fossil Reptiles of Southern Germany. 



