The Osteology of tlie Scombrid?e. 79 



Postclavicle in two parts. 



Parapoplajses never developed far anteriorly; when they appear 

 they soon become attached to form hiemal arches and spines at about 

 the middle of the abdominal cavity. 



Eibs posteriorly at the tips of the abdominal haemal spines, each 

 pair with their bases in contact. 



The epipleurals never borne by the ribs except in Acanthocybium, 

 • Baseosts expanded at base of dorsal spines to form broad bony 

 bucklers. 



First interhsemal never much enlarged, nor strongly attached to 

 the first haemal spine. 



United parapophyses in no way differentiated from haemal arches, 

 so that abdominal vertebrae are only distinguished from caudal verte- 

 brae by the attachment of ribs. 



Caudal rays deeply divided to receive hypural plate, which they 

 usually completely cover. 



Dorsal spines weak and flexible ; dorsal and anal with some pos- 

 terior rays detached to form finlets. 



Caudal peduncle very slender; the caudal rays very divergent. 



The principal sub-family and generic differences are indicated in 

 the following key : 



A. Pterotic not excluded from brain cavity by a deep pit behind prootic. 

 No bony caudal keel except in Sardiune. 



B. The opistbotic situated on lower surface of cranium ; not interposed 

 between the exoccipitals and pterotic ; the lower limb of posttem- 

 poral attached to its posterior edge. The myodome open behind in 

 a small transverse slit. The ethmoid produced to a strong angle 

 in front ; nasals narrow and projecting far beyond them. No 

 lateral caudal keel either bony or membranous. Suborbital ring 

 complete with a sensory tube. Scombrin.e. 



1. Gill rakers moderately long; metapterygoid not supporting ptery- 

 goid. • Scomber. 



2. Gill rakers extremely long ; metapterygoid assisting quadrate to sup- 



port pterygoid. Rastrelliger. 



BB. Opistbotic as much on superior as inferior surface of cranium, and 

 interposed between the pterotic and exoccipital ; lower limb of 

 posttemporal attached to its superior surface. Suborbital ring 

 incomplete, and without a sensory tube. 



