Plate III. 



Nautilus Pompilius. 



Fig. 1. Front view of the young, showing the cicatrix, and area of attach- 

 ment of the ovisac, the siphon, portions of the fourth and fifth 

 septa, the siphonal funnel with its abdominal channel or gutter, 

 and part of tbe side and dorsum of the continuation of the first 

 whorl, which has been left attached to the apex. The shadow 

 cast by the broken edges of the fifth septum on the upper part 

 of the siphon gives the exact outline of the abdominal cell, 

 which is bidden behind the siphon. Magnified 8 diameters. 



GONIATITES ATRATU3. 



Fig. 2. Section through the centre of the siphonal ccecum and siphon. Loc. 

 Choquier. Magnified 21 diameters. 



GONIATITES DIADEMA. 



Fig. 3. Front view of the ovisac, with a portion of the first whorl, exhibiting 

 the false abdominal lobe of the first septum, which is formed by 

 the breaking away of the ventral side of the cone of the siphonal 

 coecum. lc, first whorl ; le, first septum ; 2e, second septum. 

 " 4. Side view of the same species. Loc. Choquier. Magnified 74 

 diameters. 



GONIATITES LlSTERI. 



" 5. Section of the ovisac, which has also cut through a portion of the 

 siphonal ccecum. The approximation of the siphonal coecum and 

 cone to the shell below the first septum is clearly exhibited, and 

 a fragment of the second septum on the abdominal side. Magni- 

 fied 102.5 diameters. 



" 6. The siphonal ccecum after a further reduction of the same section. 

 The neck of the ccecum and remnant of the second septum have 

 broken away, leaving only that part of the ccecum which was 

 formed by the siphonal funnel of the first septum. The cone 

 opens freely into the siphonal ccecum. Magnified 317 diameters. 

 Loc. Choquier. 



GONIATITES CRENISTRIA PllUl. 



Fig. 7. Section of six whorls from a specimen of the variety having a flat 

 abdomen. This shows very plainly the eccentricity of the siphon 

 which is cut by the plane of the section at different levels in dif- 

 ferent parts of the specimen, and entirely cut away in the young. 

 Magnified 15.5 diameters. 

 " 8. Enlarged view of a siphonal funnel from the same, d', lining layer 

 of shell ; d", d'", median and external layers of the shell ; P, 

 siphonal funnel; s'", siphonal sheath. Magnified 104 diameters. 

 Loc. Rudesheim. 



