430 MOLLUSCA SUB-KINGDOM VI 
Class 2. SCAPHOPODA. Bronn.! 
(Cirrhobranchiata, Blainville ; Solenoconchia, Lacaze-Duthiers ; 
Prosopocephala, Stoliczka.) 
Aquatic, marine, bilaterally symmetrical Mollusks, protected by an external, 
tubular, somewhat curved and tapering shell, open at both ends, the concave side 
of which is dorsal ; the shell secreted by a mantle of the same shape, the larger, 
anterior opening of which is provided with a circular muscular thickening, the smaller 
opening serving as outlet for organie waste and genital products. Mouth furnished 
with a radula, borne on a cylindrical snout, and surrounded by a rosette of leaf-like 
appendages ; a cluster of numerous exsertile filaments (captacula) springing from its 
base. Otocysts present, but no eyes or tentacles. Foot rather long, conical, with 
lateral lobes, and adjacent to the snout ventrally. 
Gills are wanting, the general surface assuming respiratory functions. Liver 
large, bilateral ; intestine strongly folded, the anus ventral and rather anterior, and 
kidney orifices adjacent to it. Heart rudimentary, with a single chamber, Nervous 
system with well-developed ganglia united by commissures. Reproduction without 
copulation, the sexual products voided through the right kidney. 
Seaphopods are without exception marine, and for the most part inhabit 
deep water. There are no littoral species. They live embedded in mud or 
sand, with only the smaller end of the shell projecting above the surface. 
Their food consists chiefly of Foraminifera and similar organisms, captured 
by the filamentary captacula. 
The tubular, curved shell, open at both ends, is characteristic of the class, 
the tubular shells of certain Gastropods and Cephalopods being invariably 
closed at the smaller end. Some tubicolous Worms (Serpulidae) form a similar 
shell, but it is composed of two layers only, instead of three 
as in Seaphopods, the growth is more irregular, and its micro- 
scopic structure very different. 
The shell of Seaphopods increases by successive increments 
at the larger end, and at the same time loses by wear and 
absorption at the smaller end. The posterior slits or notches 
occurring in some species are therefore formed by reabsorption 
of the previously solid shell wall, and have a genesis wholly 
. different from the slits or fissures of Pleurotomaria, Fissurella, 
®@ and other Gastropods. 
Various genera described as Scaphopods have since been 
iripcion Wéeae, found to belong to the Serpulidae. Such are Pyrgopolon, Mont. 
Montf. Upper Cre- (Fig. 788), from the Maestricht of Belgium, also known as 
segons Oe™” Entalium, Defr., and Pharetrium, Konig; and Hamulus, Morton 
(Falcula, Conrad), of the American Cretaceous. The Cambrian genus Spiro- 
dentalium, Walcott, in which the shell has spiral striae, is at present too 

Fic. 788. 
1 Literature (see also, under the head of Mollusca, pp. 344, 345): 
Deshayes, G. P., Anatomie et Monographie du Genre Dentale (Mém. Soc. Hist. Nat., Paris, vol. IT. 
pp. 321-378), 1825. 
Lacaze-Duthiers, H. de, Histoire de Vorganisation et du développment du Dentale (Ann. des Sci. 
Nat. [4], vols. VI.-V III.), 1856-57. 
