Fig. 
Fig. 
Fig. 
Fig. 
.5. Diagram corresponding to fig. 4. 
.6. Intestine of 2. maculata (male), with the ventral portion of each turn of the 
SPIRAL VALVE IN THE GENUS RAIA. 61 
DESCRIPTION OF THE PLATES. 
PLATE X. 
1. Longitudinal section of the intestine of Raia, sp., made by removing the whole 
ventral half of both gut and spiral valve (an example of type A). 
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. 
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. 
4. Longitudinal section of another (dried) specimen (an example of type B). 
valve cut away. 
. 7. Intestine of another specimen of R. maculata (male), dissected in the same 
manner as fig. 6. 
. 8. Intestine of Raia, 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 a, and viewing the upper 
moiety from below. 
Fig. 10. Mucous membrane of the first turn of the spiral valve of a specimen of Raia 
maculata 3 (x6). 
. 11. The same in R. batis 2 (x6). 
Fig. 12. The same in 2. maculata 2 (x6). 
Fig. 13. The same in BR. batis 3 (x6). 
PLATE XI. 
Fig. 1. Intestine of Raia, sp., in longitudinal section (type C). 
Fig. 2. Diagram corresponding to fig. 1. 
Fig. 3. Intestine of Raia, sp., dissected similarly to fig. 7, Pl. X. (type D). 
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 Chimera monstrosa, dissected similarly to fig. 8, Pl. X. 
Fig. 7. Diagram corresponding to fig. 6. 
Fig. 8. Intestine of Zygena malleus, opened along the middle ventral line, and reflected 
Fig 
Fig 
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. 
. 9. Diagram corresponding to fig. 8. 
. 10. Transverse section through the middle of the same intestine ( X 2). 
