Plate I. 



Deroceras planicosta. 



Fig. 1. Front, or dorsal view of ovisac, with a portion of first whorl, magni- 

 fied -f- 80 diameters. A, ovisac ; U, umbilicus ; le, first septum ; 

 2e, second septum ; R, siphonal coecum ; O, siphonal fissure. 



" 2. Abdominal side of same specimen. 



" 3. Section of the same, the ovisac worn down somewhat, and the fir6t 

 whorl split off still lower, giving section of siphonal coecum. D, 

 Shell ; S, beginning of true siphon. 



<( 4. Side view of the same, showing also the third septum 3e. Magni- 

 fied 123 diameters. 



" 5. Dorsal view of another specimen, magnified -f- 80 diameters. 



" 6. Abdominal side of another specimen; lc, first whorl; X, lines in 

 the interior, probably indicating sutures made by the intersection 

 of first septum, or siphonal coecum with the shell of the first whorl. 

 Magnified -|- 80 diameters. 



" 7. Same specimen before being so completely reduced ; only the sides 

 of the older whorls are worn down, admitting the light to the ex- 

 posed portion of the ovisac, and the embryonal umbilicus. Magni- 

 fied-80 diameters. 



" 8. Another specimen with the septal outlines for four and a quarter 

 whorls. Magnified 21 diameters. 

 All of the above, from 1 to 8 inclusive, were taken from the same 

 block of dark blue limestone. Loc. Wiltshire, England. 



GOXIATITES FECUNDUS. 



" 9. Young of circular variety. Barrande. Ceph. Bohemia. Plate 



XI. Fig. 2. 

 " 10. Young of elliptical variety. Ibid., Plate 



XI. Fig. 4. 



GONIATITES AFTER SANDBERGER'S FIGURES. 



Fig. 11. Young Gon. compressus. Sandberger, Jahrb. d. Nass. Verein. 1851, 



p. 15, PL III. 

 " 12. Young Gon. subnautilinus. Sandberger, Jahrb. d. Nass. Verein. 



1851, Fig. 27. 

 " 13. Young Gon. canaliculars, var, gracilis. Sandberger, Jahrb. d. Nass. 



Verein. 1851, Fig. 28. 

 « 14. Young Gon. sublamellosus. Sandberger, Jahrb. d. Nass. Verein. 



1851, Fig. 29. 

 " 15. Young Gon. lamed, var. latidorsalis. Sandberger, Jahrb. d. Nass. 



Verein. 1851, Fig. 30. 

 " 16. Young Gon. lamed, var. calculiformis. Sandberger, Jahrb. d. Nass. 



Verein. 1851, Fig. 31. 

 "17. Young Gon. planorbis. Sandberger, Jahrb. d. Nass. Verein. 1851, 



Fig. 32. 

 " 18. Young Gon. diadema. Sandberger, Jahrb. d. Nass. Verein. 1851, 

 Fig. 33. 



