2? 



the hinge, and is oblong (the length being about double the width) convex below, flat-concave 

 above, truncated at both extremities, and here somewhat hollowed out. 



The animal (fig. 31) has both lobes of the mantle grown together, with exception of 

 an aperture for the foot, and 2 siphonal apertures. The aperture for the foot is (see fig. 

 35) situated a little before the middle of the animal's length, and is elliptical (in the direction 

 of the animal's axis) with continuous edge, occupying about V 3 of the animal's length. 



The siphonal apertures are circular, sub-sessile; the branchial (fig. 31 b) not at all 

 prominent, the anal (a) only a little prominent like a short conical tube. The branchial 

 siphonal aperture (fig. 36. 39 b) is large, and its edge surrounded by a circle of 12 propor- 

 tionally lurge, couically tapering, or awl-shaped tentacles (ibid. t. t.). These tentacles are 

 (see fig. 40) pinnate, or show on each side 45 short blunt lateral branches, which like the., 

 whole outermost narrower or tapered part of the tentacles are covered with small prolonged 

 awl-shaped soft papillae (fig. 41). 



The anal siphonal aperture (tig. 36, 39 a) is small, scarcely half as hirge as the bran- 

 chial, and without tentacles; but the siphon itself is (see fig. 32) everywhere thickly covered 

 with fine taper-pointed papillge, (fig. 34). Its aperture, as could be clearly seen in living 

 specimens, is not perfectly round, but rather heart-shaped (fig. 33) the lower wall of the 

 siphon being somewhat incurved in the middle. 



A row of 16 small papillge (Y 2 V 3 of the size of the branchial tentacles) which are 

 simply conical, forms round both siphons or along the posterior edge of the mantle, an oval 

 border elevated in the direction of the animal's height (fig. 36. 39 xx). 



The body (fig. 37. 39. 42) is roundish or trapezoidal, strongly inflated and of white 

 color. The foot which is also white, proceeds (fig. 42 d) from, or a little before, the middle 

 of the ventral side of the body; it is shaped, as it were, like a knee at the base, forming 

 nearly a right angle with the body, and is otherwise extended forwards ; it is slender, cylindro- 

 conical, slightly compressed at the sides and rounded at the extremity. It is, when contrac- 

 ted, scarcely half as long as the animal, but has, when extended in the living state (fig. 

 31. d) a length nearly equal to that of the animal itself. On its ventral side near the 

 basis, it has a slight medial longitudinal groove, whence proceeds a long, but very thin lyssus, 

 (fig. 35 i.) consisting of extremely fine parallel tendinous, or strongly transparent and colorless 

 threads. About the anterior half of the dorsal side of the animal is occupied by a glandular 

 mass which fills the hollow of the umbones of the shell, (in the individual examined, the 

 ovary) (fig. 37 o.o.) and consists of tolerably large globular hyaline cseca or capsules (fig. 38) 

 attached to a very short and slender cylindrical stem, and each of which has a globular or 

 oval yellowish white egg enclosed in, but far from filling its cavity. In the smaller eggs the 

 globular nucleus was very evident: in the larger, it had disappeared. Under the ovary lies the 

 reddish brown liver. 



The gills, of which there is apparently only one on each side of the body (fig. 42 e) 



are light-brown, elongated, and curved nearly in a cresent-like form: in the posterior free 



4* 



