AND CLASSIFICATION OF THE HETEROPODA. 17 



but the two lateral uncini present only the relative character of being compara- 

 tively long and slender. 



Cardiapoda (D'Orb.) 



Looking upon Cardiapoda pedunculata, carinata, caudina, and placenta 

 (figured respectively in DOrl. Voy. Amer. Merid., t. 11, figs. 5, 3, and 4 ; and Voy. 

 la Bonite, t. 17, f. 11, 1-5), as probably the same species, I am at a loss to know 

 what I should call my species, which is evidently the same thing. 



My first specimen, of which I immediately made a drawing (Plate I. fig. 10), 

 was obtained in the S.W. Pacific, and scarcely exceeded f inch in length. The 

 muzzle was much fuller and more cylindrical than that of Firoloides, and the 

 buccal mass equalled about one-third of its extent. The eyes were remarkably 

 broad, and closely resembled those of Carinaria and Oxygyrus. They were 

 fronted by simple conical tentacula. The auditory sacs were visible through the 

 stout integument at some little distance behind the eyes. 



The muscular sheath of the body exhibited a close and even tissue round the 

 snout, head, and neck ; but, on approaching the position of the foot, it formed 

 itself into a number of longitudinal linear bundles, which passed, on the one 

 hand, into the pedicle of the viscera, and, on the other, into the tail. 



The propodial foot (Plate I. fig. 10, g) crested the middle of the ventral sur- 

 face, and on its posterior border it bore the mesopodial disc (Plate I. fig. 1 0, h), 

 which was laterally bilobed, and more highly developed than it is either in Firo- 

 loides or Firola. 



The tail {metapodium) was rather remarkable in its appearance. Thus, being 

 at first cylindrical, it soon exhibited a subterminal enlargement, from which again 

 it suddenly tapered into a lengthy filiform appendage (Plate I. fig. 10, k). The 

 enlargement just noticed was convex above, corresponding with the position of 

 the operculum in Atlanta and Oxy gyrus, while its inferior surface was expanded 

 into a kind of disc, with a jagged, prominent ring-like border, densely coated 

 with black pigment (Plate I. fig. 10, i). The use of this organ is yet unknown 

 to me, but it appears to be homologous with the peculiar structure above de- 

 scribed, as occurring on the under surface of the metapodium of Atlanta. 



The whole extent of the visceral nucleus, shell, keel, and all, scarcely equalled 

 the expansion of the foot ; and the internal organs in general were so invested 

 with pigmentary matter that the heart (Plate 1. fig. 10, m) was the only one 

 distinctly apparent at a cursory glance. 



Numerous branches (Plate I. fig. 10, n), with a plain external surface and a 

 zig-zag internal fold, protruded from beneath the dorsal lip of the shell, which 

 was semicartilaginous, shallow, or scoop-shaped, with an involute nucleus, and 

 a deep but very thin and delicate keel. 



The external male organ (Plate 1. fig. 10, o) resembled that of Carinaria, con- 



VOL. XXIII. PART I. E 



