12 



ARKIV FOR ZOOLOGI. BAND 4. 



n:o 25. 



The second artery in the last named form has joined the third 

 just at its entrance into the circulus (Fig. 8 c). 



In Spheroides arteria carotis externa (Fig. 8 c, ce) arises 

 from the circulus cephalicus cranially to the first efferent 

 branchial artery, close to the entrance of this vessel into the 

 circulus. Whether there is a connection between the exter- 

 nal carotid and the branch of the hyoidean artery marked 

 with * in Fig. 9, I cannot state with certainty. Adopting 

 Allen's terminology the part of the circulus that runs for- 

 wards after having given off the external carotid forms the 

 internal carotid. Arteria carotis interna represents in Sphe- 

 roides distinctly the glosso-internal type (Allis). In Sphe- 



■ceA- 



. £/riC 



.UJ^/Ui 



^ 



f 



Cm. 



r^ 



Fig. 8. Circulus cephalicus of Lactophrys trigonus (a), Dioden holacan- 

 thus (6) and Spheroides testudineus (c). 



ce, a. carotis externa ; on, a. orbito-nasalis ; ci, a. carotis interna, ene, 

 a. encephalica; cer, a. cerebralis. Other reference letters as in Fig. 7. 



roides it divides rather soon in arteria orbito-nasalis (Fig. 8 c, 

 on) and a7'teria encephalica (Fig. 8 c, ene), which joined with 

 the corresponding artery of the other side gives off the cere- 

 bral arteries (Fig. 8 c, cer). A connection corresponding to 

 that between the circulus and the pseudobranch stated by 

 Parker to be present in the cod I ha ve not found in Sphe- 

 roides. 



Arteries arising from the ventral e?ids of the efferent bran- 

 chial arterics. These arteries I ha ve studied only in Sphe- 

 roides testudineus, mainly on a series of microscopical slides. 

 The detailed course of these vessels is known only in a few 

 Teleosts, which renders it difficult to make any comparisons. 

 Except Parker's figure of the cod, we have hardly more 



