MOLLUSCA. 9 



The dissection of the specimen was commenced by laying open the mantle along the 

 median line of the ventral or infundibular aspect to near the border of the posterior fossa 

 from which the shell began to protrude. On divaricating the divided mantle, the parts were 

 exposed which are shown in fig. 11 ; viz., the base of the funnel, with its two narrow, elon- 

 gated articular cavities {g g), the linear elevations on the inner surface of the mantle corre- 

 sponding thereto^'j/); the membranous and muscular tunic, h, enveloping the liver, perfo- 

 rated on each side posteriorly by the pallial nerve-trunks, which immediately swell into the 

 pallial ganglions, i, fig. 1 2 and 1 3 ; posterior to which ganglions the bases of the gills are 

 attached ; and, in the ventral interspace of these, there is a low conical prominence with 

 three valvular apertures : the middle one, of an infundibuliform anus, k, fig. 1 2, and on each 

 side a more minute orifice (I) with a plicated prominent border. Behind the base of the left 

 gill, n, a fourth orifice at the extremity of a short tube (m, fig. 12), also communicates with the 

 branchial or external compartment of the pallial cavity. The branchial chamber showed no 

 trace of a muscular or membranous septum (" bride anterieure," Cuv. in the Octopods). The 

 gills {n ri) have the usual elongated narrow triangular form : each is supported on a fleshy 

 stem, extended along its outer border, perforated by the branchial artery, and connected to 

 the walls of the branchial chamber by a duplicature {n", fig. 13) of the delicate lining mem- 

 brane, which is reflected upon the basal half of the stem, and invests the whole complex gill : 

 the base of the stem itself is attached to the septum dividing the branchial from the peri- 

 cardial and visceral chambers. Each gill consists of about twenty -four pairs of plicated folds 

 extended between the fleshy stem, and the trunk of the branchial vein that traverses the 

 opposite or inner border of the gill. The principal venous trunks (o, fig. 13) of the general 

 system, enter the peritoneal compartments on each side the rectum, and there develope the 

 venous follicles, in the form of irregular puckered subelongate bulgings out of their coats, 

 which give a spongy aneurismal character to their trunks ; they unite into a single trunk on 

 each side, which enters a small branchial heart, p, with an appendage. The branchial artery 

 is continued directly into the fleshy stem. The branchial veins, q, pass behind the spongy 

 veins, and terminate in the outer ends of a transversely elongated fusiform ventricle, r, from 

 which a large anterior and small posterior aorta is given off. 



Directing my attention, next, to the mass covered by the muscular investment, h, I slit 

 up the funnel and exposed the small terminal valve, c, fig. 14, and raising the valvular base 

 of the funnel, removed, first, the covering formed by the lining membrane, and exposed the 

 longitudinal fasciculi of the muscular tunic, h, fig. 14. On dissecting away this, as on the 

 left half in fig. 14, the corresponding lobe of the liver was shown, as at s. On removing 

 the whole of the muscular investment, together with the funnel, the parts were exposed which 

 are shown in fig. 15. The liver consists of two lobes, distinct from their anterior apices (ss) to 

 near their opposite ends : here they had been torn, so that whether they were distinct throughout 

 or not, I could not determine. On divaricating them, as in fig. 15, the oesophagus, t, was seen 

 penetrating their interspace, with the aorta and the trunk of the visceral nerve. Behind the 



