812 



VARIATION AND REGENERATION. 



Once a very abnormal shell was presented to me at Ralum in New Britain, in 

 which the shell was divided into two nearly equal halves by a submedian raphe, re- 

 minding one of the shell-slit of Pleurotomaria. The raphe extended back over the 



Fig. 15. Malformed shell of N. 



involuted coils of the shell, and I am unable to decide whether it was due to an 

 injury to the mantle or to some congenital malformation. 



