COMPARATIVE ANATOMY. 



41 



of the last chamber, and then periodically builda up a wall 

 I. .-inn.! it by the secretion from the hind part of tho body. In 

 t :,. iKuitihiH the edges of the partition between the two chamber* 

 lire |il:iiu. hut in tho amuiouitoH these edges are BO folded M to 

 present very complicated and beautiful patterns when viewed 



from which the water flows, after being received through some 

 lit* in the side*, into the chamber in which the gill* are lodged, 

 is split down it* whole length. This funnel is situated on the 

 opposite Hide of tho head to the hood, so as to occupy the outer 

 side of the shell mouth. Tho mouth has two jaws, which are of 





VL 



PTEROPODA : I., I'. SHELLS or HTALEA. II. ANIMAL IN ITS SHELL (DIACRIA). III. HTALEA COMPLANATA, DEAWK AS THOUGH IT WXRB 



TKANSPARENT, TO SHOW THE VISCERA, ETC. CEPHALOPODA : IV. LOLIOO, A DECAPOD ACETABUL1FEBOUS GENUS. V. OCTOPUS VULGAKIS, THB 

 POULPE OPENED TO SHOW THE ARRANGEMENT OF THE ORGANS. VI. SUCKER FROM THE ARM OF A SEPIA. VI'. THE SAME IS SECTION, TO 

 SHOW THE PISTON AND THE MUSCLES WHICH RETRACT IT. VII. SlDE VlEW OF THE GANGLIONIC KING OB CENTRAL NKBVOUS ST3TBM 



OF SEPIA. VIII. SIDE VIEW OF AN IMPERFECT AMMONITE, SHOWING THE NOTCHED SUTURE. IX. SIDE VIEW OF SAME. X. RESTORED 

 BELEMNITE AND ITS SHELL. 



Refs. to Nos. in Figs. Ill 1, 1, fins or wings; 2, 2, mantle which lines and also overlaps the shell; 3, month; 4, stomach ; 5, intestine ; 

 6, liver ; 7, ventricle of heart ; 8, auricle of ditto ; 9, ascending vessel which gives branches to the fins ; 10, gills ; 11, ganglion, giving nerves 

 to fins and mantle. V. 1, 1, 1, 1, roots of the arms, which are cut short; 2, 2, mantle thrown back ; 3, funnel, or locomotive pipe ; 4, bucc&l 

 mass; 5, crop; 6, stomach; 7, blind sack opening into the stomach; 8, intestine; 9, arms; 10, 10', auriclet; 11, ventricle; 12, gill heart 

 (there are two of these, but the left is concealed); 13, 13, vena cavoe veins leading direct to the branchial hearts ; 14, spongy masses round 

 venae cavee, supposed to be kidneys ; 15, ovary; 16, 16', oviduct ; 17, ascending aorta, or main trunk. VII. 1, suprn-CBeophageal ganglion ; 

 2, sub-cesophageal ganglion (anterior) ; 3, ditto (posterior); 4, 5, upper and under mouth ganglia; 6, nerves in arrnsj 7, ditto to mautle; 

 8, ditto to eye ; 9, buccal mass ; 10, throat. 



from the outside. Tho head of the nautilus is but little distinct 

 from the body, and from its upper side the mantle is developed 

 into two folds. One of these adheres to the shell, and the other 

 is puckered into a kind of hood, which falls as a kind of door to 

 close the opening of the shell when the animal retires within it. 

 This thickened part is also nsed to crawl upon. The funnel, 



a shelly structure, and this is surrounded by a multitude of 

 feelers, all of which can be retracted into sheaths. These 

 animals have four gills instead of two, and they have no ink- 

 bag ; otherwise, their internal structure is not unlike the other 

 class. 



The Dibranchiato cephalopoda are of higher organism than 



