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great 'probability that the shell- covered forms of all kinds which 

 have the protoconch — namely, the ancient and modern Gastro- 

 poda, Tentaculites, and the ancient Pteropoda, and all the radical 



Fig. 7. 



Tig. 3.— Aspect of the apex of the conoh m Ortfi. unguis Phill., after the protoconch has 

 been shed in the usual manner, b, oonoh or shell of the apex ; c, cicatrix. 



jrjg. 4.— Aspect of the apex, after the protoconch has been accidentally broken off, frac- 

 turing the outer shell, and exposing the cicatrix, b c, as before. 



Figs. 5-7.— Apex and protoconch of Orth. elegcms JNIunst. from the front, side and above. 

 a, protoconch ; b, shell of apex. 



Figs. 8, 9.— Another individual, said to be of the same species, less magnified, a b, as 

 before. The author has also, in Spy. crotalum, traced the striae of the outer shell on 

 the protoconch itself, showing the continuity of the shell over this part (a), and 

 completing the evidence that it must have been the shell which enclosed the em- 

 bryo, and could not have been a mere plug, as asserted by Barrande (Syzt. sil, 

 pi. 488). (See Figs. 10 and 11, p. 361). 



