SYNOPSIS OF THE PRINCIPAL GRORPS. 107 
bent backward, so that the two openings are approxi- 
mated; nervous system one or two ganglia, with sim- 
ple branches, placed between the openings of the ali- 
mentary canal. 
Potyzoa. Mouth surrounded by ciliated tentacles. 
BRACHIOPODA. Body enclosed in a bivalve shell; 
mouth with two long cirriferous arms. 
Catalogue of the Mollusca of New Zealand.—Hutton, Geological 
Survey Department, 1879. 
MOLLUSCA.—Body unsegmented. Lower portion of the 
integument developed into a foot; the upper portion 
produced into a mantle. Nervous system a gangliated 
cesophageal ring, and one or more visceral ganglia, 
united to the cesophageal ganglia by commissures. 
Heart dorsal, consisting of a ventricle, and one or two 
auricles. 
LAMELLIBRANCHIATA. Body enclosed in 2 bivalve 
shell; no head. 
SCAPHOPODA. Body vermiform ; head rudimentary. 
PTEROPODA. Swimming by two anterior fin-like ex- 
pansions of the foot. 
GASTEROPODA, Head distinct ; creeping by means of 
a foot. 
CEPHALOPODA. Head distinct; mouth surrounded by 
eight or ten fleshy arms. 
Critical List of the New Zealand Shells.—Von. Martens, Geol. Survey 
Department, Wellington, 1873. 
Catalogue of the Mollusca of New Zealand.—Hutton, Geol, Survey 
Department, Wellington, 1879. 
Catalogue of the Tertiary Mollusca and Kchinodermata.—Hutton, 
Geological Survey Department, Wellington, 1873. 
