64 



with r, the fleshy stem entire, the dotted Ime indicating the passage 

 of the branchial artery into it. 

 q . The smaller branchia of the left side. 

 s. s. The common stem of the branchiae, by which they adhere to the inner 

 surface of the mantle. 



10. 10. The branchial veins. 



11. 11. The valves placed at their terminations in 



t. The ventricle, or systemic heart, laid open. 



12. The origin of the lesser aorta. 



13. The artery of the glandular ovarian apparatus. 



14. The siphonic artery. 



15. The artery of the intestine. 



16. The larger aorta. 



16'. Its muscular origin, or the continuation of the ventricle. 



17. The valve at the extremity of this part. 



Fig. 2. A lamina of the larger branchia magnified, showing its subdivisions 

 into the smaller laminae. The letter and figures indicate the same parts as in 

 fig. 1. 



PLATE VII. 



Fig. 1. The ner^^ous system oi Nautilus Pompilius. 



a. a. The cut-surfaces of the hood, as at e, plate 4. 



b. b. The open ends of the digitations. 



c. Four of the digital tentacles exposed by laying open the canals in 

 which they are lodged. 

 d. d. Tlie anterior ophthalmic tentacles similarly exposed at their origins. 

 e. The left external labial process : (the corresponding one on the right 

 side has been removed.) 

 /. /. The internal labial processes. 

 g. The olfactory laminae. 



h. The external labial tentacles of the left side, with their origins exposed 

 by laying open the canals at the anterior part of the process in 

 which they are lodged. 

 i. The internal labial tentacles of the left side similarly exposed. 



