464' University of California Publications in Zoology [Vol.22 



ventral wall to the posterior hepatic orifice which it enters (pi. 22. 

 figs. 1, 2, 3). After circling the lumen of the posterior liver, it emerges 

 at the dorsal edge of the orifice and passes posteriorly and ventrally 

 into the intestine. Its fate there will be described in connection with 

 the latter organ. From the hepatic orifice to the intestine, a small 

 ridge lies opposite the free edge of this typhlosole. The gastro- 

 intestinal typhlosole is ciliated throughout its entire length. 



A second fold, which we may call the gastric, typhlosole (g. t.), 

 originates in the dorsal caecum (pi. 23, figs. 6, 7), passes above the 

 opening of the oesophagus, and, running parallel to the previously 

 described typhlosole, extends to the posterior hepatic orifice where it 

 ends (pi. 22, figs. 1, 2). A low, ciliated ridge (c. r.) parallels its free 

 edge and continues on above the hepatic orifice and down to end 

 beneath the right one of the two folds lying in the caecal orifice (pi. 23, 

 fig. 6). 



Between this ridge and the one accompanying the gastro-intestinal 

 typhlosole is a row of small, transverse folds in the wall of the stomach 

 (pi. 22, fig. 1). They extend from the posterior end of the gastric 

 typhlosole to the fold under which the ciliated ridge ends. From the 

 other (left) fold in the caecal orifice, around to the right fold, in a 

 spiral course, is another row of more pronounced wrinkles and pockets 

 (pi. 22. fig. 1; pi. 23, fig. 6). The appearance of these on the outside 

 of the stomach is shown in plate 23, figure 7. The function of these 

 two rows of irregular corrugations, which are of practically constant 

 occurrence, is probably to increase the surface or the capacity of the 

 stomach. 



There is a small ridge, or lip. above and below the opening of the 

 oesophagus into the stomach. The ventral one extends some distance 

 to the left between the dorsal caecum and the lateral pouch. 



Cilia do not cover the whole interior of the stomach as in more 

 generalized bivalves, but are restricted to definite regions. The ciliated 

 ridge and the gastro-intestinal typhlosole have been mentioned as 

 being ciliated, but the ciliary mechanism of the alimentary tract has 

 not yet been fully worked out in Teredo as it has by Nelson (1918) in 

 several other forms. A few observations on living animals, however, 

 have shown strong, localized, ciliary currents, and further investiga- 

 tion will probably disclose an elaborate mechanism for handling and 

 sorting food homologous with that found in other species. The method 

 of manipulating the wood chips which are ingested would of itself 

 be an interesting discovery. 



