4 ARKIV FÖR ZOOLOGI. BAND 7. N:0 30. 



Balistes. B. vetula L. (Fig. 3), wbich I have dissected, 

 shows the anterior part of the intestine of an equal width 

 quitelike the condition in Triacanthus. There is no trace of 

 dilatation. The mucous membrane of the oesophagus forms 

 longitudinal folds (oe), which continue into the network of 

 the stomach (Pl. IT, Fig. 3 st). The stomach ist distinguished 

 from the duodenum {du) by a transverse fold. Not far from 



Fig. 3. Balistes vetula L. a anus; ai. b. airbladder; d. h- ductus hepaticus; 



oes oesophagus; p pectoral arcli; pcZ postclaviculare; pe pelvicbone; 



st stomach; v. sp. ventral spine. 



this pyloric val ve the hepatic du et enters into the duodenum 

 {dp, Fig. 3). The duodenum is characterized by a network of 

 folds of the mucous membane with larger meshes than in the 

 stomach. 



Monacantlius. Within this genus the development of an 

 air-sac seems to begin. M. occidentalis Gthr. does not show 

 any dilatation. The stomach is of equal width (Fig. 4 st). 

 But in other species we find a dilatated stomach. Thilo has 

 examined M. setifer and 31. trossulus. The former species 



