370 KAIIAKICHI KISmXOUVE: 



does Dot unite with the Cuvierian duct directly. In tlüs genus most of the 

 segmental veins running along the haemal spines in the precaudal region and 

 also in the anterior pai't of the caudal region are divided into many venules 

 near the veiiebral column, so that their blood does not return directly to the 

 heaii, but seams to be collected to venules above the vertebral column and in 

 the dark red portion of the lateral muscle. This is very remarkable. The 

 segmental veins in the caudal region unite to a slender caudal vein. 



In NeotJmnnvs the posterior cardiiuJ vein is Tery conspicuous, and gives 

 off a peculiar plexus in the haemal canal, and at last joins the right Cuvierian 

 duct. The cutaneous veins are united by an anterier ti'ansverse commissm'e as 

 in Pdrathunnus, or sometimes each of them pour directly into the Cuvierian 

 duct of the respective side as in Thunnus. A shoit slender renal vein rims 

 under the iX)sterial cardinal vein and is rmited to it. 



In the IvatsuTvonidae the vertebral venous system consists of the posterior 

 cardinal vein, jugular veins, Cuvierian ducts, lateral veins, cutaneous veins, 

 segmental veins, and subspinal plexus. The posterior cardinal vein is con- 

 nected with a remarkably well developed plexus of venules in the haemal 

 canal and joins the right Cuvierian duct as in the genus Neothunnus. Tlie 

 cutaneous veins do not join the Cuvierian duct directly, nor are they united 

 by a transverse vessel in the thoracic region to the postarior cardinal vein, 

 but ai'e divided to renal portals. Tlius these cutaneous veins differ fi'om the 

 similar veins of the Thunnidae. Moreover the lower cutaneous vein of this 

 family is not homologous to the lower branch of the cutaneous vein of the 

 Thunnidae. Tlie epaxial and hypaxial veins originate in different myotomes 

 and they do not form a loop at the caudal region, nor are they connected by 

 a transverse commissure. In Kcäsuivonus the epaxial and hj-paxial cutaneous 

 veins are neai'ly equal in size and length, and though they are not sti'aight 

 they ai'e neai'ly equally distant fi'om the lateral metlian hne of the body. 

 These veins rim anteriorly and to a deeper part of the body, passing thi'ough 

 the myotome of the fifth vertebra. The epaxial vein passes l)elow the fii'st rib, 

 while thj lower passes above it. These two veins receive blood respectively 

 fi-om the sheets of vascular plexus on the dorsal and ventral sides of the dark 

 red portion of the lateral muscle. In the other genera, Erdhynnvs and Auzis, 

 the epaxial cutaneous vein is very thick and inins close and parallel to the 



