Myxinid The mouth of the hagfish (Figure 9-27) is super- 

 ficially like that of the lamprey, but the funnel is without 

 teeth and papillae. There are four pairs of tentacles around 

 the funnel, and a nasohypophyseal opening lies above it. 

 There is a rasping organ, in the floor of the mouth cavity, 

 armed with two semicircles of teeth, the anterior set larger 

 than the posterior. There is a single tooth in the roof of the 

 mouth above the rasping organ. 



The nasohypophyseal canal opens into the mouth poste- 

 riorly, and behind this junction there is an enlargement of 



the pharynx, the velar chamber. From the roof of this 

 chamber a velum is suspended from a midline frenulum. 

 The lateral margins of this structure can be rolled and un- 

 rolled to produce a pumping action driving water back 

 through the pharynx. The branchial pouches open to either 

 side from the pharynx which leads back to the intestine. 



The intestine is a straight tube of large diameter. There 

 is no typhlosole, but the inner walls have longitudinal folds, 

 as in the lamprey. The liver has a posterior left lobe and an 

 anterior ventromedial lobe; the lobes are not joined (Figure 



follicles of ova 



pancreas 



gastrohepotic artery 

 liver 



ostium of both oviducts 



esophagus . 



opening of bile duct- 



spiral valve 

 nidamental gland 



superior mesenteric vein 

 superior mesenteric artery 



spleen 



inferior mesenteric artery 



abdominal pore 

 opening of seminal vesicle 



B 



opening of MLillerian duct 

 urinary pore 



lin urogenita 



I sinus 



Figure 9-25. Viscera of Hydrolagus. A, ventral view; B, lateral view of gut with the left wall cut away 

 to reveal the interior. 



THE DIGESTIVE TRACT AND ASSOCIATED STRUCTURES • 277 



