SPIRAL VALVE IN THE GENUS EAIA. 61 



DESCRIPTION OF THE PLATES. 



PLATE X. 

 Fig. 1. Longitudinal section of the intestine oi Raia, sp., made by removing the whole 



ventral half of both gut and spiral valve (an example of type A). 

 Fig. 2. Diagram of spiral valve corresponding to fig. 1, constructed by representing the 

 course of the attached edge by a thick line, and that of the free edge by a 

 thin line. 

 Fig. 3. Transverse section through the bursa entiana of another specimen, showing the 



way the valve is rolled upon itself in the first part of its course. 

 Fig. 4. Longitudinal section of another (dried) specimen (an example of type B). 

 Fig. 5. Diagram corresponding to fig. 4. 

 Fig. 6. Intestine of B. maculata (male), with the ventral portion of each turn of the 



valve cut away. 

 Fig. 7. Intestine of another specimen of R. maculata (male), dissected in the same 



manner as fig. 6. 

 Fig. 8. Intestine of Baia, sp., with the ventral wall of each compartment removed, the 



valve being left intact (type C). 

 Fig. 9. Obtained by cutting the same intestine across the line ab, and viewing the upper 



moiety from below. 

 Fig. 10. Mucous membrane of the first turn of the spiral valve of a specimen of Baia 



maculata S (x6). 

 Fig. 11. The same in B. batis ¥ (x6). 

 Fig. 12. The same in B. maculata ¥ (x6). 

 Fig. 13. The same in B. batis d ( X 6). 



PLATE XL 



Fig. 1. Intestine of Baia, sp., in longitudinal section (type C). 



Fig. 2. Diagram corresponding to fig. 1. 



Fig. 3. Intestine of Baia, sp., dissected similarly to fig. 7, PI. X. (type I)). 



Fig. 4. Diagram corresponding to fig. 3. 



Fig. 5. Intestine of Scyllium canicula ¥ (half nat. size). Dissected similarly to fig. 3. 



Fig. 6. Intestine of Chimwra monstrosa, dissected similarly to fig. 8, PI. X. 



Fig. 7. Diagram corresponding to fig. 6. 



Fig. 8. Intestine of Zygwna malleus, opened along the middle ventral line, and reflected 

 to right and left (in consequence of this the intestine appears much wider 

 than it really is) ; the ventral portion of each turn of the scroll-valve cut away. 



Fig. 9. Diagram corresponding to fig. 8. 



Fig. 10. Transverse section through the middle of the same intestine ( X 2). 



