SEA-FISHERIES LABORATORY 



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The fifth thoracic arthrophragm (Text fig. 5, B.) 

 arises between the fifth and sixth thoracic somites. All 

 the parts are very similar to those described in the fourth 

 arthrophragm. The sternal border is slightly more 



A, 



C, 



Fig. 5. — Anterior view of the left side of thoracic arthrophragms. 



A. = 4th thoracic arthrophragm. B. = 5th thoracic arthrophragm. 



C. =6th thoracic arthrophragm. D. = 7th thoracic arthrophragm. 



(The parts are shaded as in Fig. 4). 

 <7.= line of fusion with the following arthrophragm. 

 h. =line of fusion with the 3rd thoracic endopleurite. 

 Jc. =line of fusion with the 4th thoracic endopleurite. 

 I. =line of fusion with posterior face of the preceding thoracic endosternite. 

 m. = antero-lateral extension of pleuro-sternal muscle chamber. 

 n. =line of fusion with the 5th thoracic endopleurite. 

 o. =line of fusion with the 6th thoracic endopleurite. 

 p. =line of fusion with the 6th thoracic endosternite. 



arched. The apodemal foramen is not quite so large. 

 There is an additional cavity left in the dorsal side of the 

 endosternite at each side (m.) This is formed by the 



