BLOOD-VASCULAR SYSTEM OF THE LORICATI 121 



sac of a branch of the internal ju<jular with one of the external 

 jugular. A sinus-like vessel connects the two internal jugulars 

 in the eye-muscle canal. A small vein connects the posterior 

 encephalic veins directly behind the cerebellum. The ventral 

 intercostal veins anastomose dorsally with the main intercostal 

 veins. The c^H-bladder veins unite on the surface of the blad- 

 der, and there are connecting vessels between the right pyloric 

 c^ca vein and intestinal vein^^. There is always some communi- 

 cation between the two portals : either they terminate in a com- 

 mon portal as is the case with Scbastodcs and Anoploponia, or 

 terminal branch (a) of the left portal unites with the right portal 

 as in Hcxagrammos^ or else there is a connecting vein in the 

 neighborhood of the spleen as in Ophiodon and ScorfcBnichthys. 

 If a posterior mesenteric vein is present as in Ophiodou and 

 ScoTpxBuichthys there is a grand anastomosis on the posterior 

 or cardiac end of the stomach of branch Z of the posterior 

 mesenteric with the right, left, and posterior gastric veins ; and 

 branch Yof the posterior mesenteric, usually, anastomoses with 

 intestinal vein^,). The anterior spermatic veins in Sebastodes 

 unite with the posterior or spermatic vein proper, and in Scor- 

 ■pcBuichthys the left gastric vein anastomoses with the ventral 

 gastric vein. 



In all the specimens studied there was the so-called choroid 

 gland in the eye, a double vaso-ganglion or retia mirabilia, and 

 a double retia mirabilia is also present in the air-bladder of 

 Sebastodes. 



The arrangement of the vascular and the blood vessels in the 

 pseudobranchial filaments is essentially the same as in the 

 branchial filaments, and it seems reasonable to suppose that the 

 arterial blood for the eye receives additional oxygen in its course 

 through the pseudobranchial capillaries. 



Sttmmary of the Arteries. — The carotids in all species 

 studied, but Aiioplopoina, rise from a common trunk, which 

 soon separates into the external and internal carotids. In 

 Anoflofoma each of the carotids rises directly from the first 

 efferent branchial artery. In every case the internal carotid 

 divides into the orbito-nasal and encephalic arteries. In all the 

 genera but Anoplopoma the main stem of the external carotid 



