96 Edwin Cliapin Starks, 



is no opening into the myoclome along the posterior edge of the lateral 

 process of the parasphenoid as in Anxis. 



The greatest difference between Euthynnns and Thnnnus lies in 

 the condition of the inferior vertebral processes. There are 20 

 abdominal vertebrae, and a like nnmber of candal, or a total of 41 with 

 the hypnral, the abdominal and caudal regions being more evenly 

 divided than in Auxis. The lower processes of the vertebrse differ 

 from those of Auxis in that the inferior foramen that is typically 

 through the base of the hsemal arch is here enormously developed, 

 while the haemal arches themselves have developed to even a greater 

 degree. The postero and antero-zygopophyses share equally in form- 

 ing long slender processes between the haemal arches. The arches 

 spring almost directly from the body of the vertebrae, and the largest 

 are as wide as the length of a vertebra and over twice that long. The 

 longest diameter of the largest of the inferior foramina is considerably 

 greater than the length of a vertebra. The first parapophysis 

 appears on the eighth vertebra, and is scarcely developed, but the 

 succeeding ones quickly attain a great length. Only four pairs are 

 developed before they unite in haemal arches. The first six or seven 

 haemal arches are broadly rounded at the lower median line, but pos- 

 teriorly a haemal spine is developed. 



The ribs and epipleurals and their attachment to the vertebrae are 

 as in Auxis. The caudal keel is as wide, but is not developed so far 

 forward. The other vertebral processes, and all of the other elements 

 not here mentioned are essentially as in Auxis. 



AUXIS. 

 A specimen of Auxis tliazard (Lacepede), from Japan, 9 inches in length. 



The supraoccipital crest is as in Thnnnus or Sarda, but the tem- 

 poral crests run less obliquely, and merge into the general level of 

 the supraorbital rim without reaching the orbital edge. The pterotic 

 crest runs more on top of the cranium and forms less of the lateral 

 cranial outline. There is a well marked depression running along each 

 side of the supraoccipital crest from the front of the frontal to the 

 epiotic as in Sarda and Thnnnus. The myodome opens posteriorly in 

 a very large round opening where the basioccipital and parasphenoid 



