OPISTHOTIC 

 PTEROTIC 



PARIETAL 

 SPHENOTIC 



PARASPHENOID 



DERMETHMOID 



PARETHMOID 



SUPRAOCCIPITAL 



EPIOTIC 



EXOCCIPITAL 



FIRST VERTEBRA 



FiouRK 2. — Skull of ThuiiniiH alaUinga. Dorsal view. jThe piiioal foramoii is iiiconcctly labeled as parietal foramen. 



bones. In life these foramina are covered by a tough 

 membrane and are not passages for nerves or blood 

 vessels. We were unable to determine their function. 

 Fronto-parietal foramina arc characteristic of Thun- 

 nus, Euthynnus, and Katsuwoniui, and the bone is 

 thin in this area in several other scombrids. 



There is a prominent medial pineal foramen 

 between the edges of the frontal bones, just anterior 

 to the supraoccipital crest. Rivas (1954a) has sug- 

 gested that in 7'. Ihijnnus light can pass through the 

 transparent "window" in the skin over this foramen 

 and then down to the brain through the carti- 



laginous lens that fills the foramen in life. He 

 postulated that the pineal ajjparatus has a photo- 

 tropic function involved in migration. Holmgren 

 (1958) also studied the pineal apparatus of T. 

 Ihynmts but could find no evidence of a photorecep- 

 tive role for the pineal organ. The pineal foramen 

 is characteristic of the more advanced members of 

 the Scombridae and is absent or represented by only 

 a small slit in the more primitive genera such as 

 Scomber, Raslrdligcr, and Scomberomorus (Allis, 1903; 

 Kishinouyo, 1923; Mago Leccia, 1958). 



Specific Characters. — Four neurocranial cliaracters 



ro 



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