THE AMPHINEURA bib) 
General Description. —The mantle covers the whole body, 
and is clothed by a rather thick cuticle, in which are implanted 
spicula (Fig. 35) developed from the tegumentary epithelium. The 
foot is nearly aborted or wanting. The nervous system consists of 
four great longitudinal trunks, with pedal and pedo-pallial anasto- 
moses. The digestive tract is straight, the Aplacophora being carni- 
vorous. The bloodisred. The gonads are in open continuity with 
the fore part of the pericardium. The coelomo-ducts, corresponding 
to the renal sacs of the Polyplacophora, are gonaducts, and open 
externally into a posterior cloacal chamber, which serves as a 
rudimentary branchial cavity. There are two groups of Aplaco- 
phora : the Neomeniomorpha and the Chaetodermomorpha. 
parE 
| 
A B 
Kia. 35. 
Spicules of various Aplacophora. A, Neomenia (Wiren); B, Donidersia (Hubrecht); C, 
Paramenia (Pruvot); D, Proneomenia; HE, Stylomenia (Pruvot); F, Myzomenia (Pruvot); G, 
Chaetoderma (Wiren). i.c, internal cavity. 
Sus-ORDER 1. NEOMENIOMORPHA. 
Aplacophora with a distinct longitudinal ventral groove ; bi- 
sexual, with paired genital glands and without differentiated liver. 
I. EXTERNAL CHARACTERS. 
The mantle extends over the sides of the body so as to cover 
the greater part of the ventral surface, leaving only a narrow 
median longitudinal furrow uncovered. The pallial cuticle, which 
is very thick in some species, contains a number of long, hollow, 
calcified, acicular, or flattened spicules (Fig. 35) borne on epithelial 
papillae. In some cases, when it is very thick, the cuticle also 
includes sensory papillae. A small longitudinal projection in the 
ventral furrow is the vestige of the foot. The antero-ventral region 
of the body is occupied by a large mucous gland, whose secretion is 
poured into a ciliated pit in the anterior part of the ventral furrow, 
the whole structure corresponding to the embryonic pedal gland of 
some Chitones. Smaller mucous glands are also found along the 
pedal projection. Posteriorly there is a terminal cloacal or branchial 
cavity, into which opens a thick mucous gland, situated between 
the foot and anus. 
