Über Lebendbeobachtungen an Caudofoveata (Mollusca, Aculifera), nebst Bemerkungen zum system der Klasse

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Abstract
Three new species, Falcidens crossotus gen. et sp. nov., F. sagittiferus sp. nov., and Scutopus ventrolineatus gen. et sp. nov. of the little known class Caudofoveata (formerly Aplacophora-Chaetodermatidae), discovered in fjords near Bergen, are briefly described and observations made on living material are reported. These investigations, the first since Wirén (1892a) and Heath (1904, 1911), concern locomotion, respiration, and heart activity. Burrowing is achieved in the first species by movements of a peristaltic nature involving the anterior part of the body only, aided by hydrostatic pressure from the lymphatic pumps; the caudal part of the body plays no part in locomotion. The two ctenidia in the terminal pallial cavity respire by means of ciliary activity of the epithelium; movement of the ctenidia themselves was observed only in connection with the beating of the heart. It is stated that the rate of heartbeat is related to temperature, and under normal conditions it varies from 19 to 21 beats per minute in Scutopus ventrolineatus, from 25 to 30 in Falcidens sagittiferus, and from 27 to 32 in F. crossotus; diastole is a clearly defined action and may be very rapid, while systole always takes place slowly. Finally there are some notes on body size and on survival under artificial conditions and, in addition to remarks concerning the determination of Crystallophrisson nitidulum, a key for the Caudofoveata genera is given.