CHAPTER IV 
THE SCAPHOPODA 
CLASS III.—SCAPHOPODA, Bronn 
(= SoLENoconcHA, de Lacaze-Duthiers). 
Definition.—Marine bilaterally symmetrical Prorhipidoglosso- 
morpha ; the body and shell elongated along the antero-posterior 
axis and nearly cylindrical. The right and left margins of the 
mantle are united ventrally and thus form a complete tube sur- 
rounding the body, but with an anterior and a posterior aperture. 
The head is somewhat rudimentary and devoid of eyes, but bears 
two dorsal appendages furnished with numerous long filaments 
(Fig. 183, I). The foot is cylindrical and adapted to digging. A 
radula is present, but there is no ctenidium. The sexes are separate. 
fistorical.—These animals were formerly mistaken for tubicolous 
Annelids, and afterwards were classed among the Gastropoda, near 
Fissurella, Blainville, in 1819, was the first to rank them as a 
distinct order of Gastropoda under the name “ Cirrhobranchia.” 
In 1857 de Lacaze-Duthiers, as the result of a careful anatomical 
investigation, created the division Solenoconcha to receive Dental ium, 
making his new division equivalent to Lamellibranchia, and includ- 
ing the two groups, together with the Brachiopoda, in a class 
Acephala. Since de Lacaze-Duthiers’ memoir, the Solenoconcha 
have been universally recognised as a division equivalent to the 
Lamellibranchia and Gastropoda, but the name Scaphopoda, proposed 
by Bronn in 1862, has been more generally used for the sake of 
uniformity. More recent investigations, however, have shown that 
the Scaphopoda are more nearly akin to the Gastropoda than to 
the Lamellibranchia. 
I. GENERAL DESCRIPTION AND EXTERNAL CHARACTERS. 
The shell (Figs. 181, D, E and 186) has the form of a very 
elongated cone, slightly curved, the concavity of the curve being 
dorsal: it is capable of containing the entire animal. The larger 
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