418 TRANS. OF THE ACAD. OF SCIENCE. 
In mammals, the gustative or hypophysial, and optic or chi- 
asmal block-pieces are distinct from the rest, and underlie, 
precisely, their respective Bask-ilabs, — in Fishes the first 
or condylar and the last or piers ctory bases remain isolated, 
jo exists as lamina sarpendivatara Brees lis, the 
rostrum sphenoidale for its block ; thus proving that 5 com- 
plete neural arches participate in the Sormation of the cra- 
nial cavity, besides the temporals. 
ExtTreMITAL Fasrics. 
In many Fishes, both pairs of extremities are con, 
with the facial and maxillary ones at the head. Like the ere 
nial vertebra, they are five in number; a foremost, ptt 4) 
nee ay or fin. The extrem ital flor! consi aC 
blade, a bar, and a (coracoid) brace,—the fuleral ee 
€ pte maxillary extremity the swan’s skull 0" 
a fine exemplification : a rok pterygoid lent 
rior prong implanted into the id cavity as | 
bears a slender, zygomatic Wade, is backed by @ St, 
and bears a pte internal humeral, meeting 
erwise naked sku — from either side, en 
al sesamoids, often ex o 
The firs" op hae Ws Okie extremity we find in pt 
ness of a bat’s hands, in the lake her 
_ allongée, Esox lencth 5 feet). 1! ic bones a | 
_ tinated t othe ma vere sean hen oe 
