125 
HALL 20. 
VERTEBRATE ZOOLOGY. 
Entrance from Hall 19. 
ICHTHYOLOGY. 
Case 58. — First and lowest class of Vertebrates, the Tuni- 
catUy or sea-squirts, represented by several beautiful glass mod- 
els. In the same case, on the next shelf above, is a single repre- 
sentative of the class Marsipobranchii, the River Lamprey. 
Cases 58 and 59. — ^The first group of true fishes (Class 
Pisces), the sub-class Elasmobranchii, or sharks and rays. Of 
the sharks here shown, the Mackerel Shark is the largest. The 
specimen of Hammer-headed Shark illustrates the strange modifi- 
cation of the head found in its family. The Tiger Shark is from 
the Indian Ocean, and in life is one of the most beautiful of the 
Sharks. The Angel Shark by its broad flattened form shows an 
approach to the next group, the Rays. 
The two specimens of Rhinobatus are quite shark-like in gen- 
eral form ; but their place among the rays is indicated by the 
position of their gill-slits. The Electrical Ray {Torpedo) is broad 
and flat, and has a smooth skin. The typical rays are represented 
by only a single specimen. One of the most interesting of the 
group of rays is Uro^ymnus from the Indian Ocean. 
Case 60. — In this case are the two remaining sub-classes of 
Pisces {Ganoidei and Teleostei). Only three species of Ganoids 
are represented; the Lake Sturgeon, the Long-nosed Gar of the 
freshwaters of North America, and Polypterus from the Nile, all 
representatives of very ancient types of fishes. Among the bony 
fishes shown some of the most interesting are : the sword-fish, the 
dolphin, the goose-fish, with its enormous mouth, and Murcena 
helena, a favorite fish among the ancient Romans. A large elec- 
tric eel from South America is displayed. There is also a 
