126 Transactions, —Zoology. 
filaments and the eye peduncles: filaments three on each side.  Dentition. 
—Central tooth rather broader than long, not oblique, reflexed portion ser- 
rated on both sides at the base. Cutting-points of laterals and inner mar- 
ginals denticulate on outer edge only, those of the outer marginals denticu- 
lated on both sides. 
The specimen figured was collected at Sumner. 
Dıtoma corrosa, Adams (= D. hectori, Hutton). Pl. XV., fig. D. 
Animal the same as D. undulosa. Dentition—Central tooth much 
broader than long, oblique, sloping posteriorly to the right. Cutting-points 
of laterals and inner marginals denticulated on the outer edge only, those of 
the outer marginals on both sides. 
The specimen figured was collected at Sumner. It is, I think, only a 
variety of the last species. 
Ditoma rLUMBEA, sp. nov. Pl. XV., fig. x 
Shell turbinate, imperforate, rather depressed, rough, sometimes with a 
few obsolete spiral ribs; whorls four or five ; spire acute but usually eroded; 
colour bluish-purple, the eroded apex whitish. Interior white, iridescent, 
the throat with shallow grooves, aperture margined with a black band; 
columella impressed, curved, sometimes with a small anterior tooth. Axis 
'9; breadth -68. Animal like D. athiops, the foot being margined with 
2 band of black and white transverse stripes. Dentition.— Central tooth as 
in D. corrosa. Cutting-points of lateral teeth denticulated on both sides. 
Cutting-points of inner marginals denticulated on outer edge only, those of 
the outer marginals on both edges. 
The specimen figured was collected at Sumner. The shell is not easy 
to distingush from some varieties of D. undulosa which has the same 
station, and the central tooth is like that of D. corrosa, but the animal and 
the lateral and marginal teeth are like D. aethiops. It is found usually in 
sheltered bays or estuaries, but sometimes on exposed rocks. I have 
collected it at Sumner and the Ocean Beach, Dunedin, and I have also 
seen specimens from Campbell Island. 
Dirowa excavata, Adams. Pl. XV., fig. r. 
Dentition.—Central tooth broader than long, not oblique, the reflexed 
portion denticulated all along the edge; the cutting-points of the laterals 
and all the marginals are denticulated on both edges. 
The specimen figured. was collected by Mr. T. F. Cheeseman at North 
Manukau Heads, 
oma (?) subRosrRATA, Gray. Pl. XV., fig. c. 
Dentition.—Central tooth broader than long, not oblique, the reflected 
portion strongly denticulated on each side and eared. Cutting-points of 
lateral teeth slightly denticulated on each side ; those of the inner marginals 
