MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 149 



the funnel, which are really fundamentally different parts of the organ. In the first place, we 

 notice the valve of the funnel projecting from the dorsal wall near the tip. (Fig. 6, V.) This is a 

 thin, tough, tongue-shaped structure precisely like the valve of the funnel of Loligo. The line 

 of attachment of the valve is exactly transverse to the axis of the funnel and is about 3 centimeters 

 from the tip of the funnel. The valve itself is 2.25 centimeters in length by 1.5 centimeters in 

 breadth at the base. In preserved specimens the valve is directed forward and lies closety pressed 

 against the roof of the funnel. Halfway between the base of the valve and the posterior end of 

 the funnel are two white lines in the roof of the funnel which approach each other like the sides 

 of a V. (Fig. ti. C.) The point of the V (which is directed backward) is not complete, as the 

 posterior and inner ends of the lines remain separated by a distance of about 5 millimeters. The 

 lines are 3 millimeters in width and 2 centimeters in length. They are. caused by the superficial 

 position of the ventral limbs of the cartilage, which here lie almost immediately beneath the 

 epithelium of the funnel, allowing the white cartilage to show plainly through the thin overlying 

 tissues. There is a marked difference in the appearance and structure of the funnel anterior to 

 these lines and posterior to them. The anterior portion is smooth, and light in color. It is 

 composed mostly of elastic tissues; small bundles of muscles form a quite definite layer upon the 

 outer side just under the epithelium, while there are only scattered muscles upon the inner side 

 of this portion. The part of the funnel in front of the arms of the cartilage is that which has 

 already been referrod to as free from the body. It is freely movable, but evidently only slightly 

 contractile. The attachment of the funnel to the body begins anteriorly on a line passing through 

 the middle of the white lines on the internal surface of the funnel. 



The part of the funnel back of the processes of the cartilage is composed entirely of muscle, 

 and is often in a state of extreme contraction in preserved specimens. The darker color of this 

 part readily distinguishes it from the anterior part. The roof of the posterior part of the funnel 

 is attached to the body along a median strip T millimeters in width and extending to the back edge 

 of the roof of the funnel. The crura;, being attached to the nuchal surface by their anterior and 

 inner edges, meet the anterior end of the attachment of the funnel and form the outer sides of 

 two deep pockets lying between them and the roof of the funnel and the median attachment of 

 the latter to the body. These lateral pockets are very similar to the pockets, or valves, beside 

 the funnel of Loligo. The attachment of the roof of the funnel to the body forks posteriorly, 

 often leaving quite a pocket above the median portion of the roof of the funnel. From the ends 

 of the fork two ribbons of skin, each attached by one edge, run back along the ventral surfaces 

 of the shell muscles for a distance of 30 to 35 millimeters. They may be 2 or 3 millimeters in 

 height at their anterior ends, but gradually diminish in height until they disappear. 



The posterior portion of the funnel possesses an internal layer of longitudinal muscles extend- 

 ing from the posterior sides of the limbs of the cartilage to the posterior edge of the funnel. 

 The external la3'er of oblique and transverse muscles is continuous with the muscles of the crura, 

 which seem to branch on the sides of the funnel, part of their muscles passing on to the sides 

 and ventral part of the funnel and part passing into the roof of the funnel. The roof of the 

 funnel might almost be described as a shelf extending between the crura. If the funnel is formed 

 in the same way in Nautilus as in the Dibranchiata whose development has been observed, the 

 roof of the funnel really consists, in large part, of a portion of the ventral surface of the body 

 folded in between lateral ridges. 



The crura are composed of the same dark muscle as the posterior part of the funnel. The} - 

 form strong muscular bands, which, attached to the sides of the nuchal region by their anterior 

 and inner edges, extend upward and backward close to the stalks of the eyes and immediately 

 back of and under the auricles of the hood. (Fig. 1, CR.) Their upper ends are attached along 

 the dorsal edges of the shell muscles and extend back to the posterior limit of the mantle cavity 

 at these points. It will be remembered that the mantle cavity is most shallow above the shell 

 muscles, being scarcely more than 10 millimeters in depth. The sides of the crura turn outward 

 and backward. They thin out gradually from the attached borders to the free edges, so that the 

 latter are thin, sharp, and pliable. Similarly, the overlapping edges of the funnel, with which 

 the free edges of the crura are continuous, are thin and tit so closely against one another that 



